Genomic DNA of human cholesterol 7α-hydroxylase and methods for using it

ABSTRACT

Genomic DNA of cholesterol 7α-hydroxylase and a minigene are disclosed. The minigene is used for making a transgenic animal that produces functionally active cholesterol 7α-hydroxylase and functions as a disease model. A cholesterol 7α-hydroxylase promoter region and reporter gene construct is provided, as well as a transgenic animal that expresses the promoter/reporter gene.

This application is a continuation of application Ser. No. 08/361,458, filed Dec. 21, 1994, which is a continuation of Ser. No. 08/135,488, filed Oct. 13, 1993 both abandoned.

Work related to subject matter described in this application was provided by research supported in part by NIH Grant GM 31584.

CROSS REFERENCE TO RELATED APPLICATIONS

U.S. Ser. No. 135,510 (Attorney Docket No. 18748/176 "TRUNCATED HUMAN CHOLESTEROL 7α-HYDROXYLASE, METHOD OF PRODUCTION AND USE THEREOF" to Chiang, J.; and U.S. Ser. No. 135,511 (Attorney Docket No. 18748/175) "CHOLESTEROL 7α-HYDROXYLASE GENE REGULATORY ELEMENTS AND METHODS FOR USING THEM" to Chiang, J. are both filed concurrently herewith and incorporated by reference in their entirety. Additionally, the present application is related to U.S. Ser. No. 08/361,458, filed Dec. 21, 1994, which is a continuation of U.S. Ser. No. 08/135,488, filed Oct. 13, 1993, and U.S. Ser. No. 08/187,453, filed Jan. 28, 1994.

BACKGROUND OF THE INVENTION

High serum cholesterol is commonly associated with an increased risk of heart attack, atherosclerosis and circulatory disorders. In addition, a variety of diseases are caused by disorders of cholesterol catabolism, such as gallstone disease, atherosclerosis, hyperlipidemia and some lipid storage diseases.

The major pathway for disposal of cholesterol in the body is by secretion of cholesterol and bile acids into the gut. Bile contains free cholesterol and bile acids. The enzyme, cholesterol 7α-hydroxylase (CYP7), commits cholesterol to bile acid synthesis and catalyzes the first and rate-limiting step of bile acid synthesis in the liver. Specifically, CYP7 catalyzes, in the presence of reductase and a reducing agent such as NADPH, the initial hydroxylation of cholesterol at the 7α-position, thereby forming 7α-hydroxycholesterol. Thus, by increasing synthesis of bile acids, this enzyme plays a key role in the liver by depleting hepatic cholesterol pools, resulting in increased LDL uptake and a lowering of serum cholesterol levels.

Bile acids are physiological agents which are important in the solubilization of lipid-soluble vitamins, sterol and xenobiotics. Bile acids are synthesized exclusively in the liver and are secreted to the intestines where they are modified to secondary bile acids. Most bile acids are reabsorbed in the ileum and recirculated to the hepatocytes via the portal vein.

The feedback of bile into the liver is known to inhibit cholesterol 7α-hydroxylase and thus inhibit the overall rate of bile acid synthesis. Cholesterol 7α-hydroxylase therefore has been a subject of intense investigations to elucidate the regulatory mechanisms of bile acid synthesis in the liver.

It is known that an interruption of bile acid reabsorption, such as that caused by the bile sequestrant, cholestyramine, or by a bile fistula, stimulates the rate of bile acid synthesis and cholesterol 7α-hydroxylase activity in the liver. It is believed that cholesterol 7α-hydroxylase activity in the liver is regulated primarily at the gene transcriptional level by bile acids, cholesterol, hormones, diurnal rhythm and other factors.

Generally, the regulation of eukaryotic genes is thought to occur at several locations, including the promoter sequences, which are located upstream of the transcription start site; enhancer or repressor sequences, which are located upstream of the promoter; within intron sequences, which are non-coding sequences located between exons or coding sequence; and in 3' sequences, which are located downstream from the coding region. The promoter sequence is unique to each gene and is required for the accurate and efficient initiation of gene transcription. Enhancers and/or repressors regulate promoter activity and determine the level of gene transcription during the development and differentiation of a particular tissue.

The promoter of most eukaryotic genes contains a canonical TATA box that binds a TFIID TATA box binding protein. TFIID complex and associated transcription activators (TAFs) interact with the basal initiation factors and RNA polymerase II to activate the promoter. The transcription complex assembly and initiation are regulated by transcription factors bound to enhancer elements located in the promoter and other regions of the gene (Pugh and Tjian, J. Biol. Chem. 267, 679-682, 1992). Tissue-specific transcription factors and nuclear steroid hormone receptors are known to play an important role in the regulation of gene expression in different tissues during development and differentiation.

However, the mechanisms underlying the regulation of cholesterol 7α-hydroxylase gene expression at the molecular level are not understood. An understanding of the regulation of CYP7 gene expression would permit development of therapeutics for treating patients with defects in bile acid synthesis and cholesterol metabolism due to altered (deficient or excessive) gene expression.

In order to study the mechanism of regulation of human cholesterol 7α-hydroxylase at the molecular level, it is therefore important to determine the correct coding, non-coding and promoter region gene sequences. An elucidation of the enzyme's gene structure, a method for analyzing promoter and enhancer/repressor activity, as well as transgenic animal models with which to study human cholesterol 7α-hydroxylase, are desired. Attempts to provide a transgenic animal expressing recombinant CYP7 have not been successful using the cDNA of CYP7. Thus, important discoveries concerning the CYP7 gene and systems for studying the CYP7 enzyme's physiology, each of which aims towards the design of therapeutic drugs and the treatment of patients with defects in bile acid synthesis and cholesterol metabolism, are highly desired.

To understand the structure and function of human CYP7 and its regulation by factors, such as bile acids, cholesterol and hormones, it is essential to purify the human CYP7 enzyme. However, the CYP7 enzyme is present in an extremely low levels in human liver; therefore, it has not been possible to isolate sufficient quantities of purified, functional enzyme from human livers.

Although a cDNA molecule encoding human CYP7 enzyme has been determined, recombinant expression of human CYP7 has not heretofore been achieved. Karam and Chiang, Biochem. Biophys. Res. Commun. 185: 588 (1992). Recently, a strategy to express a catalytically active, truncated rat cholesterol 7α-hydroxylase in E. coli was disclosed. Li and Chiang, J. Biol. Chem. 266 (29): 19186 (1991). The disclosures of both of those publications are expressly incorporated herein by reference. In the latter publication, it was disclosed that the expression of a membrane-bound hydrophobic protein in E. coli is difficult because the bacteria lacks internal membranes. Via PCR, a modified cDNA was generated that encoded a truncated enzyme lacking the N-terminal 23 amino acid residues of the rat cholesterol 7α-hydroxylase enzyme. The resulting protein was expressed, predominantly in the cytosol of the bacteria. The purified recombinant enzyme was active, as determined by its ability to hydroxylate cholesterol in a reconstituted system, and has a K_(m) for cholesterol and V_(max) similar to those of the rat microsomal (non-truncated) enzyme.

Despite the high sequence identity between the rat and human cholesterol 7α-hydroxylase, however, it previously has not been possible to express the human cholesterol 7α-hydroxylase in E. coli following the same strategy and using the same expression vector (pKK233-2) as that previously used for the expression of rat cholesterol 7α-hydroxylase. Thus, a catalytically active, recombinant human CYP7 enzyme is desirable. Recombinantly-expressed, truncated human CYP7 could be used to detect agents that stimulate or inhibit human CYP7's catalytic activity. Further, such recombinant protein can be used to produce anti-CYP7 antibodies which would be useful for screening assays, for example, to detect stimulated or inhibited production of human CYP7 in response to exposure of a compound to a human CYP7-producing culture.

SUMMARY OF THE INVENTION

An embodiment of the invention provides genomic DNA of cholesterol 7α-hydroxylase, in particular, DNA sequences of FIGS. 4, 5, and 6, clones λHG7α26 (ATCC 75534) and λHG7α5 (ATCC 75535), and fragments thereof.

Another embodiment provides an expression vector comprising genomic DNA of cholesterol 7α-hydroxylase and a host cell comprising the vector. Further, an expression vector can comprise a construct of a cholesterol 7α-hydroxylase promoter region operably linked to a reporter gene. Such a construct can be introduced into a mammal at an embryonic stage to provide a transgenic nonhuman mammal. Thereby, advantageously, germ cells and somatic cells of the mammal contain a promoter region from the human genomic CYP7 5' flanking sequence of the human cholesterol 7α-hydroxylase gene, wherein the promoter region is operably linked to a reporter gene.

The transgenic mammal described above containing the reporter construct can be used to screen or determine an agent's capacity to up- or down-regulate the promoter region of human cholesterol 7α-hydroxylase. This is achieved by exposing the mammal to a test agent and detecting an effect the expression of reporter gene in the mammal relative to that of a control, where no agent is applied. For example, when the mammal is exposed to agents that upregulate the promoter region of human cholesterol 7α-hydroxylase, expression of reporter gene is increased, and the agent is identified as potentially capable of decreasing serum cholesterol in humans.

Another embodiment of the invention provides a transformed cell comprising a recombinant human cholesterol 7α-hydroxylase gene which is operably linked to a cis-acting regulatory element that controls expression of said gene and wherein the recombinant human cholesterol 7α-hydroxylase gene sequence is substantially the same as the coding sequence of human cholesterol 7α-hydroxylase gene.

Another embodiment provides a cell, wherein transcription of recombinant human cholesterol 7α-hydroxylase gene is under the control of cis-acting regulatory elements/promoter that are the same as the sequences controlling the transcription of the endogenous human cholesterol 7α-hydroxylase gene, and wherein a cis-acting regulatory element controlling transcription of said gene is inducible.

Another object of the invention is to provide a cholesterol 7α-hydroxylase minigene for transforming an animal to produce functionally active cholesterol 7α-hydroxylase. A minigene of CYP7 in this context can comprise exons I through VI inclusive and at least two introns selected from the group consisting of I and II; and I, II and III. Optionally, the minigene can further comprise a CYP7 promoter region.

Another transgenic nonhuman mammal is provided according to the invention, the mammal having germ cells and somatic cells that comprise a recombinant human cholesterol 7α-hydroxylase gene that is operably linked to a cis-acting regulatory element that controls the expression of the gene in said mammal such that peripheral blood cholesterol levels and the production of bile acids in said mammal are affected. The gene is introduced into said the non-human mammal or an ancestor of the non-human mammal at an embryonic stage, and a chromosome of said mammal includes an endogenous coding sequence substantially the same as the coding sequence of the human cholesterol 7α-hydroxylase gene. Such a transgenic mammal is provided, wherein transcription of recombinant human cholesterol 7α-hydroxylase gene is under the control of those cis-acting regulatory elements/promoter sequences that control transcription of the endogenous human cholesterol 7α-hydroxylase gene, and wherein the cis-acting regulatory element controlling transcription of said gene is inducible.

Another embodiment of the invention provides catalytically active, truncated human cholesterol 7α-hydroxylase (CYP7). Advantageously, the truncated human CYP7, which can be produced recombinantly and in relatively large recoverable amounts, has a specific activity that is at least a substantial fraction of the specific activity of truncated rat enzyme produced in accordance with Li and Chiang, J. Biol. Chem. 266 (29): 19186 (1991).

Another embodiment of this invention provides a catalytically active, truncated human CYP7, which lacks a membrane anchor region that is present in human CYP7. Advantageously, amino acids 1 to 24 of the membrane anchor region are deleted.

Other embodiments provide analogs of the catalytically active, truncated human CYP7 proteins of this invention.

Another embodiment comprises a fusion protein comprising catalytically active, truncated human CYP7, or a portion thereof, and a structural protein in addition to the truncated human CYP7. Advantageously, the structural protein is capable of ready expression in a particular host system such that production of truncated human CYP7 can be increased by virtue of the increased production of the structural protein.

Other embodiments provide DNA encoding the foregoing catalytically active, truncated human CYP7 proteins.

Other embodiments of the invention provide an expression vector and a host cell useful for recombinant expression of catalytically active, truncated human CYP7.

Yet other embodiments provide a method for producing catalytically active, truncated human CYP7, comprising the step of culturing a host cell according to this invention under conditions which permit production of catalytically active truncated human CYP7.

Another embodiment provides an antibody which specifically recognizes an epitope of catalytically active, truncated human CYP7.

Another embodiment provides a method for screening a compound for its effect on expression of non-truncated human CYP7. The method comprises the steps of (a) providing a host cell according to the invention under conditions which permit production of catalytically active truncated human CYP7, (b) contacting the host cell with a compound and (c) detecting the amount of catalytically active, truncated human CYP7 expressed by the host cell.

Another embodiment provides a method for screening a compound for its effect on non-truncated human CYP7 enzyme activity. The method comprises the steps of (a) contacting catalytically active, truncated human CYP7 with a compound and (b) measuring the catalytic activity of the catalytically active, truncated human CYP7.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A shows a gene map of the human CYP7 gene, while FIG. 1B and FIG. 1C show the gene map of clones λHG7α26 and λHG7α5, respectively. Exons I, II and III are represented by shaded boxes. Arrows indicate regions where sequences have been determined (shown in FIGS. 4, 5 and 6).

FIG. 2 is a diagrammatic representation of the construction of the human cholesterol 7α-hydroxylase containing plasmid, pH7aMG. Shaded thin boxes represent amino acid coding exons, while vector is represented by shaded thick boxes. A 5.5 kilobase EcoRI fragment (FIG. 4) which contains promoter region, exons I, II and partial exon III and introns I and II, was fused to a EcoRI-XhoI fragment of cDNA which contains partial exon III, exons IV, V and partial exon VI. An internal EcoRI site in exon III provided the linkage of the gene fragment to the cDNA to construct a minigene, as discussed in Example III. Restriction enzyme cleavage sites are as follows: Ba=BmH1, Ec=EcoR1, E=EcoR V, Sc=Sca 1, B=Bgl 11, Xb=Xba1, H=HinD111, C=Cla 1, P=Pst 1, Xh=Xho 1, S=Sma 1, K=Kpn 1.

FIG. 3 (SEQ ID NO:8) shows a human CYP7 amino acid sequence that is expressed in a transgenic animal carrying a minigene.

FIGS. 4A-4F show (SEQ ID NO:9) a nucleotide sequence, including exon I, intron I, exon II, intron II and exon III, of human CYP7.

FIGS. 5A-5B shows (SEQ ID NO:10) a nucleotide sequence, including 5' upstream Eco RI fragment.

FIGS. 6A-6B show (SEQ ID NO:11) a nucleotide sequence, including intron IV exon V, intron V, and exon VI, of human CYP7.

FIG. 7 is a diagramatic representation of the construction of the luciferase reporter gene vector that includes the 5' sequence from the human genomic cholesterol 7α-hydroxylase gene, and the reporter luciferase gene described in Example 2. Restriction enzyme cleavage sites are as follows: K=Kpn 1, E=EcoR1, Sc=Sca 1, Bg=Bgl 11, Xb=Xba 1, H=Hind 111, X=Xho 1, B=BamH 1, Sa=Sal 1.

FIG. 8 (SEQ ID NO:4) provides the cDNA sequence of human CYP7. The ATG start codon is located at positions 29-31 and the TGA stop codon at positions 1475-1477.

FIG. 9 illustrates a recombinant expression vector construct for truncated human cholesterol 7α-hydroxylase cDNA. Nucleotides 1-46 of SEQ ID NO:4 are also shown in this Figure. The PCR-generated cDNA, H7α1.5, was inserted in an NcoI digested expression vector pJL, as described in Example 1. Abbreviations are as follows: Transcription enhancer (T.E.), ribosome binding site (R.B.S.), Xba I and NcoI (restriction enzyme sites), M (methionine), A (alanine), R 25! (arginine, residue 25 of full-length protein); G (glutamine). In the vector, restriction enzyme sites, the ampicillin resistance gene (Amp), the origin of replication of PUC12 (Ori PUC12) and the tac promoter (ptac) are indicated.

FIG. 10 illustrates a Lineweaver-Burke plot of activities of truncated human and truncated rat cholesterol 7α-hydroxylase in E. coli. Truncated CYP7 activity was measured using a reconstitution assay, such as that described in Example 10, at different concentrations of cholesterol, as indicated. Linear regression was used to draw the line.

FIG. 11 (SEQ ID NO:5) provides the truncated human CYP7 amino acid sequence.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention relates to the isolation and sequencing of the human genomic CYP7 gene, including intron and exon sequences and 5' upstream sequences. Two clones containing genomic CYP7 DNA are sequenced, as shown schematically in FIGS. 1B and 1C. The invention also includes a recombinant vector containing at least a fragment of the genomic CYP7 gene and a host cell, such as E. Coli, containing the vector.

The invention further includes "fragments" of the CYP7 genomic DNA, exemplified by a DNA fragment that is an exon or intron of the CYP7 gene. In FIGS. 4A-4F, exon I is nucleotides 2236 to 2319, intron I is 2320 to 3928, exon II is 3929 to 4169, intron II is 4170 to 5210, and exon III is 5211 to 5537. In FIGS. 6A-6B, partial exon IV is 1 to 456, exon V is 457 to 632, intron V is 633 to 1220, and exon VI begins at 1221 of FIGS. 6A-6B. The category of "fragment" within the present invention also encompasses any fragment obtained by digesting the disclosed DNA of the invention with any restriction endonucleases, preferably, at the restriction sites shown in FIG. 1. Other restriction fragments can be obtained as well, by using conventional skills in the art.

Also encompassed by the present invention are DNA sequences that hybridize under stringent conditions, preferably high stringent conditions, with any of the DNA sequences or fragments mentioned above. According to the present invention the term "stringent conditions" means conditions with a salt concentration of 4× SSC (NaCl-citrate buffer) at 62°-66° C., and "high stringent conditions" means conditions with a salt concentration of 0.1× SSC at 68° C.

From the determined gene sequence of human CYP7, a promoter region of the gene is further identified. Clone λHG7α26 contains an insert that spans about 8.0 kb of the 5'-upstream flanking sequence. According to the invention, this sequence information permits construction of a human CYP7 promoter operably linked to a reporter gene. This "promoter/reporter" gene construct is used to transform host cells and animals. For example, the promoter/reporter gene is used to transform E. coli strain JM101 or mammalian hepatocytes, or to transform a transgenic mouse or hamster.

In another embodiment of the invention, a transformed cell line or transgenic animal containing a promoter/reporter gene according to the invention is provided. Such a transformant readily detects an agent that increases or decreases expression of CYP7 gene. This is so because the agent's interaction with the CYP7 promoter region produces a corresponding reporter protein expression pattern that is easily detectable. For example, where the firefly-derived protein luciferase is used as a reporter gene, luciferase expression is measured quantitatively by its bioluminescence.

The CYP7 promoter region or certain regulatory elements excised therefrom can be used for the controlled expression of either the CYP7 gene or various reporter or indicator genes which allow quantitative determination of gene expression in the presence of inhibitory or stimulatory drugs. Reporter genes include, but are not limited to, E. coli β-galactosidase, galactokinase, interleukin 2, thymidine kinase, alkaline phosphatase, luciferase and chloramphenicol acetyltransferase (CAT). Such an expression system can, therefore, also be used for screening compounds for their ability to inhibit or stimulate expression of a structural gene.

In another embodiment, a minigene construct is provided by ligating a fragment of newly discovered genetic information, in particular a gene sequence excised from clone λHG7α26, together with a cDNA spanning exons 3-6. According to the present invention, a minigene is provided and used to transform an animal for in vivo production of human CYP7.

In making a the minigene in accordance with the invention, a promoter region and exons I-VI are employed, as well as introns I and II, or introns I, II and III of the genomic CYP7 DNA. However, any of introns III, IV or V may be omitted. For example, introns III, IV and V, or introns IV and V of the CYP7 gene can be omitted. Thus a preferred minigene according to the invention contains all of the CYP7 exons as well as introns I and II. Another minigene according to the invention contains all exons and introns I, II and III. Therefore, a method is provided for expressing a CYP7 gene in transgenic animals that have been transformed with a minigene, such as the minigene shown in FIG. 2.

Optionally the minigene can contain the promoter region of CYP7. Alternatively, another known promoter region is substituted for the promoter region of CYP7 to permit experimentally regulated promoter-driven expression in an animal. For example, a transgenic mouse can be made wherein the CYP7 minigene is driven by the metallothionein promoter. Use of this promoter in a transgenic mouse provides a model of CYP7 overexpression in the transgenic animal.

In another embodiment of the invention, a human CYP7 minigene permits production of a transgenic animal, preferably an animal that carries new genetic information in every tissue, including the germ cells. A minigene, when introduced into a transgenic animal, will express a CYP7 protein having an amino acid sequence shown in FIG. 3. This animal is a useful disease model for screening an agent in vivo effect on the regulation of CYP7 expression, as described further in Example 3.

Various methods are employed to introduce foreign genes into animals. These methods include: micro-injection of DNA into single cell embryos, retroviral infection of embryos and calcium phosphate-mediated DNA uptake by embryonic stem cells. Hogan et al., MANIPULATING THE MOUSE EMBRYO; A LABORATORY MANUAL (Cold Spring Harbor Laboratory, 1986); Leder et al., U.S. Pat. No. 4,736,866; Leder et al., U.S. Pat. No. 5,175,383; Krimpenfort et al., U.S. Pat. No. 5,175,384, the contents of each of which are hereby incorporated by reference.

The most successful and most preferred technique is microinjection of DNA. Hammer et al., J. Anim. Sci. 63: 269 (1986); Gordon et al., Science 214: 1244 (1981); Brinster et al., Proc. Natl. Acad. Sci. USA 82: 4438 (1985). Microinjection involves the isolation of embryos at the single cell stage. The DNA encoding the gene of interest is microinjected in vitro into the isolated embryos and the manipulated embryos are implanted into pseudo-pregnant females. Transgenic animals can be identified shortly after birth by analyzing the DNA obtained from a tissue fragment, such as the tail, using probes specific for the inserted gene. Integration has been generally found to occur in a head-to-tail concatameric fashion at a single genomic site. Incorporation of the foreign gene at the one-celled stage results in a transgenic animal; if integration occurs at a multicellular stage, a mosaic results. Integration of two different embryonic stem cells may lead to the creation of a chimeric animal. Only microinjection results in the production of animals that can transmit the genetic information to their progeny in a Mendelian fashion. Germline integration is essential in order to utilize these transgenic animals as perpetual animal models.

Introduction of the recombinant human cholesterol 7α-hydroxylase gene at the fertilized oocyte stage ensures that the gene sequence will be present in all of the germ cells and somatic cells of the transgenic "founder" animal. The presence of the recombinant gene sequence in the germ cells of the transgenic founder animal means that approximately half of the founder animal's descendants will carry the activated recombinant gene sequence in all of their germ cells and somatic cells.

Several factors determine the level at which the new protein will be expressed, as well as its temporal and tissue-specific manner of expression. Perhaps the most important factors are the promoter and enhancer employed in controlling the expression of the protein encoded by the inserted DNA. Regulatory elements which are tissue-specific direct significant expression to a specific tissue; whereas ubiquitous promoters permit expression in different tissues within the animal.

Important cis-acting regulatory elements, other than the 5' upstream region, are required for expression of a human gene at levels equivalent to or higher than that in the unmodified organ. It is known that the first intron and second intron and possibly third intron of a human gene are important in the regulation of protein expression.

Furthermore, the presence of intronic sequences within the transgene have been shown to eliminate or at least dampen inhibitory effects of the site of DNA integration into the genome. Behringer et al., Science 245: 971 (1989); Lang et al., EMBO J. 7: 1675 (1988). For example, in order to overcome the positional effects of integration upon expression levels, the prior art has positioned enhancer regions 10-50 kb upstream, introns, or parts of introns close to splice junctions in the DNA constructs for transgenic animal production. Brinster et al., Proc. Natl. Acad. Sci. USA 85: 836 (1988); Buchman et al., Mol. Cell Biol. 8: 4395 (1988). Therefore, one of ordinary skill in this art, given the DNA sequence of the present invention, would be able to construct various combinations of cis-acting regulatory elements of the human cholesterol 7α-hydroxylase gene to test which regions are required for expression of the human gene at levels equivalent to or higher than that in the unmodified organ. The cis-acting regulatory elements of the human cholesterol 7α-hydroxylase gene to be used in such constructs are selected from: the 5' upstream region, the first intron, second intron and third intron of the human gene.

In general, the invention features a transgenic non-human vertebrate animal, preferably a mammal such as a rodent, eg., a mouse or hamster, containing germ cells and somatic cells that contain a recombinant gene which is substantially homologous with a vertebrate gene in the cholesterol 7α-hydroxylase family which is capable of expressing cholesterol 7α-hydroxylase. The recombinant gene is introduced into the animal, or an ancestor of the animal, at an embryonic stage, preferably the one-cell, or fertilized oocyte stage, and generally not later than about the 8-cell stage. The recombinant gene preferably is substantially homologous with (i.e., greater than 50% homologous, and preferably greater than 80% in terms of encoded amino acid sequence) human cholesterol 7α-hydroxylase.

Preferably, transcription of the human cholesterol 7α-hydroxylase encoding DNA is under the control of the promoter sequence that is the same as the promoter sequence controlling transcription of the endogenous coding sequence, so that the expressed protein is regulated similarly to its expression in humans. The term endogenous cis-acting regulatory elements refers to the nucleic acid sequence that controls the expression of a the human cholesterol 7α-hydroxylase gene in vivo.

The animals of the invention can be used as models to test for agents that potentially effect the expression of human cholesterol 7α-hydroxylase. The use of transgenic animals to test for agents that effect: (1) the expression of various enzymes involved in cholesterol metabolism and (2) atherosclerosis is well known to those of skill in the art, as described by Breslow, Proc. Natl. Acad. Sci. USA 90: 8314 (1993), the entire contents of which are hereby incorporated by reference. Since human cholesterol 7α-hydroxylase is the rate limiting enzyme controlling peripheral blood cholesterol levels, the consequent occurrence of hypercholesterolemia in humans is dependent upon the levels at which this enzyme is expressed. Hypercholesterolemia (or hypercholesteremia or hypercholesterinemia) is a clinical condition in which there is an abnormally large amount of cholesterol present in the cells and plasma of the circulating blood. Hypercholesterolemia is a serious medical condition that leads to atherosclerosis, atheromatous plaques, arteriole sclerotic plaque formation, hypertension and heart disease. The transgenic animals of the invention can be used for testing agents that may cure hypercholesterolemia, or relieve its symptoms, or for testing agents that may promote hypercholesterolemia.

The agents to be tested can be administered to an animal of the invention and the animal's peripheral cholesterol and bile acids are monitored. Peripheral cholesterol is measured by routine tests available in most clinical laboratories. Bile acid production is monitored using reverse phase high pressure liquid chromatography (HPLC).

Transgenic animals of the invention are most useful as animal models for testing agents and procedures that promote or inhibit overexpression or under expression of CYP7. Overexpression would result in increased bile acid synthesis from cholesterol whereas underexpression would result in decreased bile acid synthesis from cholesterol and hypercholesterolemia. Therefore, transgenic animals of the invention may be used to study the regulation of bile acid synthesis and hypercholesterolemia. In particular, a transgenic mouse or hamster on a high cholesterol diet is used to determine whether overexpression of CYP7 in the mice could prevent hypercholesterolemia. Transgenic mice fed a diet containing high levels of both bile acids and cholesterol are used to determine whether a high bile acid diet suppresses 7α-hydroxylase expression and thus induces hypercholesterolemia.

The constructs of the present invention may be used to assess gene expression in vitro as well as gene regulation in vivo. For example, the construct of FIG. 2 may be used to transfect hepatocytes and other mammalian cells to test for tissue specific expression of the CPY7 gene. Also, the construct of FIG. 7 may be used to transfect hepatocytes and other mammalian cells to assess the regulation of the CPY7 gene.

In general, the invention features a transformed mammalian cell, preferably a hepatocyte, containing a recombinant gene which is substantially homologous with a vertebrate gene in the cholesterol 7α-hydroxylase family which is capable of expressing cholesterol 7α-hydroxylase. The recombinant gene is introduced into the cell by various transfection means well known in the art. The recombinant gene preferably is substantially homologous with (i.e., greater than 50% homologous, and preferably greater than 80% in terms of encoded amino acid sequence) human cholesterol 7α-hydroxylase.

Preferably, transcription of the human cholesterol 7α-hydroxylase encoding DNA is under the control of the promoter sequence that is the same as the promoter sequence controlling transcription of the endogenous coding sequence, so that the expressed protein is regulated similarly to its expression in humans.

The cells of the invention can be used as models to test for agents that potentially effect the expression of human cholesterol 7α-hydroxylase. The agents to be tested can be provided to the cells and the expression of human cholesterol 7α-hydroxylase assayed. Such transformed cells are useful for testing agents that promote or inhibit overexpression or under expression of CYP7.

Analysis of the CYP7 promoter may be performed in cell culture using either the downstream recombinant CYP7 minigene or a reporter construct. The CYP7 regulatory elements can be used for the controlled expression of either the CYP7 gene or various reporter or indicator genes which allow quantitative determination of gene expression in the presence of inhibitory or stimulatory drugs. Reporter genes and systems have been described herein.

In another related discovery, it has been found surprisingly, that catalytically active, truncated human CYP7 now can be expressed recombinantly. This is achieved by using a bacterial strain having the characteristics of the E. coli strain TOPP3, and a vector having the characteristics of the expression vector pJL. No other bacteria strains or expression vectors have been found that possess the characteristics permitting expression of the truncated human CYP7 enzyme. In particular, "E. Coli TOPP3-pJL/H7α1.5" contains the expression vector pJL/H7α1.5 DNA and encodes a truncated human CYP7 cDNA that is expressed in relatively large amounts in the bacterial cytosol.

Therefore, one embodiment of the present invention is a catalytically active, truncated human CYP7 protein. "Truncated" as used herein means that a portion, all or substantially all of the complete membrane anchor region of human CYP7 has been deleted. Advantageously, all or a substantial portion of amino acids 1 to 24, which comprise the membrane anchor region in human CYP7, are deleted. FIG. 11 provides the amino acid sequence of a catalytically active, truncated human CYP7 protein in accordance with this invention.

By "catalytically active" it is meant that the CYP7 protein is capable of catalyzing, in the presence of reductase and a reducing agent such as NADPH, the initial hydroxylation of cholesterol at the 7α-position, thereby forming 7α-hydroxycholesterol. Catalytic activity can be measures in known assays using several well known parameters such as K_(M) and V_(Max). Advantageously, catalytic activity can be measured as specific activity and compared with the specific activity of the catalytically active, truncated rat CYP7 discussed above. Most advantageously, specific activity of the truncated human CYP7 and the truncated rat CYP7 are measured in simultaneously run assays under identical conditions. Otherwise, assay-to-assay variations in activity may be observed by virtue of differences in the assay conditions.

Also encompassed by the invention is an analog of catalytically active, truncated human CYP7. In accordance with this invention, the term "analog" includes a protein having conservative amino acids substitutions or deletions that do not eliminate the enzymatic activity of the truncated human CYP7. Advantageously, the analog retains a specific activity that is at least about ten percent (10%) of the specific activity of truncated rat CYP7 produced in accordance with Li and Chiang, J. Biol. Chem. 266: 19186 (1991).

Skilled artisans will readily appreciate that an analog of catalytically active, truncated human CYP7 having the amino acid sequence in FIG. 11 readily can be constructed. The analog can be the prepared, for example, by exploiting the degeneracy in the genetic code, or by effecting a point mutation which yields an amino acid substitutions and/or additions or deletions of non-essential amino acids. Advantageously, the amino acid substitutions can be conservative in accordance with well known principles.

By way of example, an analog advantageously includes those proteins having at least about 85%, and more advantageously at least about 90% amino acid sequence homology, which proteins still possesses substantially similar enzymatic activity as that of the truncated rat CYP7. Advantageously, the catalytically active, truncated human CYP7 or analog thereof will possess at least about 10%, advantageously at least about 25%, more advantageously at least about 50%, more advantageously at least about 75%, and more advantageously at least about 90% of the specific activity of catalytically active, truncated rat CYP7 as measured in simultaneous assays run under identical conditions.

The present invention further includes a fusion protein comprising catalytically active, truncated human CYP7, or a portion thereof, and a structural protein in addition to the truncated human CYP7. Advantageously, the structural protein is capable of ready expression in a particular host system. Advantageously, the structural protein is a protein which is produced in relatively high quantity by the host. In this way, production of truncated human CYP7 can be increased by virtue of the increased production of the structural protein. Thus a vector is provided that in addition to a truncated hCYP7 gene, such as H7α1.5, further contains a gene encoding at least one additional structural protein. The additional protein is advantageously selected from among proteins that are expressed at high levels in E. coli, including factor IX, for example. See Nagai et al., Meth. Enzym. 153: 461 (1987), the contents of which are hereby expressly incorporated by reference.

Additional embodiments of this invention comprise DNAs which encode the proteins described herein. Those skilled in the art will appreciate that many different DNAs can encode a single protein, and preferred codons routinely can be employed for different expression systems. All such DNAs are contemplated within this invention. Further, within this embodiment are DNA sequences that hybridize under stringent conditions, preferably under highly stringent conditions, with the DNA sequence encoding catalytically active, truncated human CYP7. According to the present invention the term "stringent conditions" means hybridization conditions comprising a salt concentration of 4× SSC (NaCl-citrate buffer) at 62°-66° C., and "high stringent conditions" means hybridization conditions comprising a salt concentration of 0.1× SSC at 68° C.

Yet another embodiment of the invention provides a method of making catalytically active, truncated human CYP7 protein recombinantly. One method comprises culturing a host cell containing the gene encoding the protein or an analog thereof, advantageously E. coli TOPP3 (ATCC 69401), under conditions which permit production of the protein. Advantageously, the method further comprises the step of recovering quantities of protein. Advantageously, as discussed below, high quantities of the polypeptide are obtained. Skilled artisans will appreciate the various ways in which recombinant proteins of this invention can be prepared.

Compared to a corresponding amount of rat CYP7 produced according to Li and Chiang, J. Biol. Chem. 266: 19186 (1991), the level of truncated human CYP7 expressed according to the invention is increased substantially, i.e., by a four-fold increase in yield. According to the present invention, a method is provided for obtaining expression of at least 30 nmol human cholesterol 7α-hydroxylase in one liter of E. coli culture, but more advantageously, 50 nmol/liter. This markedly improved yield can be achieved by subcloning the cDNA in a pJL expression vector to form pJL/R7α1.5, which can then be transformed into E. coli strain TOPP3. The pJL expression vector is characterized by possessing (i) a transcription enhancer sequence, located upstream from and proximal to a ribosomal binding site, and (ii) an origin of replication for pUC12.

Another embodiment of this invention is an expression vector containing the DNA encoding truncated CYP7, especially an expression vector additionally containing a transcription enhancer region (T.E.), particularly wherein said T.E. is located upstream from and proximal to a ribosomal binding region. Preferably, the vector also has an origin of replication for pUC12 as well, or some other origin known to be associated with the expression of high copy numbers of an inserted gene. Typically, the T.E. and the ribosomal binding region are operably attached to the truncated CYP7 cDNA. An advantageous embodiment of the present invention includes the expression vector pJL/H7α1.5 containing DNA encoding truncated CYP7 and the transfected E. coli TOPP3 (ATCC 69401) as a host cell.

Also included is a method of making a truncated CYP7 protein that employs an expression vector containing a transcription enhancer region (T.E.), particularly wherein said T.E. is located upstream from and proximal to a ribosomal binding region and which preferably has an origin of replication for pUC12. This method can be exploited to make truncated CYP7 proteins having a species origin other than human or rat. Thus, for example, hamster, murine and other species of truncated CYP7 made by using an expression vector (without the human gene insert) and an E. coli TOPP3 host cell are encompassed by the invention. In particular, according to the present invention, E. coli TOPP3 transfected with a pJL expression vector containing a CYP7 genomic insert of the desired species of CYP7 is used to produce another species of truncated CYP7.

E. coli TOPP3-pJL/H7α1.5 was deposited on Aug. 25, 1993, at the American Type Culture Collection, ATCC, 12301 Parklawn Drive, Rockville, Md. 20852, U.S.A. under the accession number ATCC 69401.

Also included in the present invention are monoclonal and polyclonal antibodies, or binding fragments thereof, specific for truncated human CYP7, i.e., which specifically recognize an epitope of catalytically active, truncated human CYP7. Methods for the preparation of such antibodies are also contemplated (see Example 11 below). Further, an anti-truncated CYP7 antibody can be used in a method to screen compounds for their ability to inhibit or stimulate CYP7 enzyme expression (see Example 11). For example, either an antibody according to the invention or an antibody against non-truncated human CYP7 is used to detect the expression of truncated human CYP7 in an assay. Thus, to screen for an agent that enhances CYP7, an agent can be added to a culture of TOPP3-pJL/Hα1.5 for a period of time sufficient for the agent to modulate expression, after which expressed truncated human CYP7 is detected using any of the above-described antibodies in a Western blot. An increase in protein content, relative to the level of control enzyme expression from cells not exposed to the agent, detects an agent that stimulates expression of human CYP7. Results of such as assay optionally are confirmed with an in vivo transgenic animal assay, as described herein.

Truncated CYP7 obtained according to the present invention also can be used in a screening assay as an indicator of non-truncated CYP7 activity. A compound can be screened to determine whether it increases or decreases either the level of enzyme expression or its activity. A compound can be tested either alone or in the presence of physiological agents or drugs (see Examples 10 and 11). Information obtained can be used to screen for potentially beneficial drugs, and particularly for the design of drugs capable of treating patients with defects in bile acid synthesis and cholesterol metabolism.

A compound screening method according to the present invention can be performed as follows. To assess a compound's effect on CYP7 enzyme activity in human liver, the compound, in varying dosages, is tested in the enzyme assay method. Such a method, is advantageously performed on truncated CYP7, purified from E. coli TOPP3-pJL/H7α1.5. A method for detecting the enzyme's activity is described in Example 10 herein. A compound's effect on CYP7 enzyme levels is determined, for example, using a CYP7 specific antibody in a Western blot assay, as described in Example 11.

The following examples illustrate the invention and, as such, are not to be considered as limiting the invention set forth in the claims.

EXAMPLE 1 Genomic DNA of CYP7 Human Cholesterol 7α-Hydroxylase

A human genomic library constructed with Sau3A1 partially digested human placental DNA ligated into a BamHI site of EMBL-3 Sp6/T7 phage vector (Clontech, Palo Alto, Calif.) was screened using a 1.6 kb EcoRI-PstI fragment of a human cholesterol 7α-hydroxylase cDNA isolated previously (Keram and Chiang, Biochem. Biophys. Res. Comm. 185, 588-595, 1992) as a hybridization probe. Hybridizations were carried out at a high stringent condition of 68° C., 1% SDS and 0.1× SSC. 800,000 pfu of phages were screened. After four cycles of screening, seven positive clones were plaque-purified. Three clones containing the largest inserts (λHG7α26, λHG7α5 and λHG7α52) were isolated and analyzed by restriction mapping. FIG. 1B shows the gene map of clone λHG7α26, which contains a 15 kb insert that spans about 8.0 kb of the 5'-upstream flanking sequence and exons I to III (FIGS. 4A-4D and 5A-5B). Clone λHG7α5 (FIG. 1C) contains intron IV, exon V, intron V and partial exon VI (FIGS. 6A-6B). An 8.0 kb 3'-flanking sequence extends beyond the sequenced region of λHG7α5 (FIG. 6).

Bacteriophage clones λHG7α26 and λHG7α5 both were deposited Aug. 25, 1993 at the American Type Culture Collection, ATCC, 12301 Parklawn Drive, Rockville, Md. 20852, USA under the accession numbers ATCC 75534 and ATCC 75535, respectively.

Five EcoRI fragments of the clone λHG26 were excised from the phage DNA insert by restriction digestion and shotgun subcloned into phagemid vector pBluescript II KS+ (Stratagene, La Jolla, Calif.). The clones were size-selected and EcoRI fragments were isolated from CsCl purified plasmids and used for sequencing. Nested deletions were generated by ExoIII/Mung Bean nuclease digestion according to manufacturer's instruction (Stratagene, Calif.) using the conditions of 37° C. incubation for 1 min intervals. This condition resulted in an average deletion of about 200 to 250 bp/min. DNA sequencing of the nested deletions were carried out by the dideoxy chain termination method using T7 sequenase version 2.0 (USB, Cleveland, Ohio) and ³⁵ S-dATP. Sequence data were obtained from both strands and the overlapping deletion clones and analyzed using DNASIS software (Hitachi America, Calif.).

Nucleotide sequences of a 5 kb EcoRI fragment and a 2.6 kb EcoRI fragments were determined. The 5 kb fragment contains the sequence from -1886 of the 5'-upstream region to partial exon 3 (FIGS. 4A-4F). Included in FIG. 4 is a 347 bp 3'-end sequence of a 3.5 Kb EcoRI fragment located immediately upstream of this 5 Kb fragment and a 233 bp 5' end sequence of a 2.6 kb EcoRI fragment immediately downstream of a 5 kb fragment. As shown in FIG. 1B, the 2.6 kb fragment (FIGS. 5A-5B) is located further 5' of the 3.5 kb EcoRI fragment. Thus, about 4875 bp of the 5'-upstream flanking region sequence of the gene were determined.

A comparison of sequences of the present invention to those of Molowa et al. (1992) in the overlapping region (1604 bp) revealed that sequences from the transcription start site to about -460 are identical; however, further upstream sequences vary significantly. A total of 52 sequence discrepancies were found, not all of are attributed to the presence of polymorphisms in the human genes. Cohen at al. (Genomics, 14, 153-161, 1992) reported a 723 bp upstream sequence. Seven mismatches in Cohen's sequence from +1 to -723 were identified. A "T" to "C" conversion at nucleotide -469 was identified to be a Mae II polymorphism (Thompson et al., Biochem. Biophys. Acta. 1168, 239-242, 1993). The 5'-flanking sequence of the present invention was identical to that reported by Thompson et al., (1993), with the exception of a mismatch at nucleotide -1197, found in the overlapping region from +1 to nucleotide -2235. No intron sequences have been reported by other laboratories.

Clone λHG7α5 was also sequenced from the 5' end of the gene. FIGS. 6A-6B is the 2316 basepair sequence that contains partial intron IV, exon V, intron V and exon VI of the human CYP7 gene.

EXAMPLE 2 Promoter/Reporter Transgenic Animal

Assessment of gene regulation in transgenic animals using the luciferase reporter system is well known to those of skill in the art. DiLelia et al., Nucl. Acids. Res. 16: 4159 (1988), incorporated by reference in its entirety. Vectors for producing such reporter constructs are commercially available from Promega Corporation (2800 Woods Hollow Road, Madison Wis. 53711-5399). For example, the pGL2-Basic luciferase vector (Promega) may be used to construct a cassette that will report the important cis-acting elements in the CYP7 5' sequence from the human genomic cholesterol 7α-hydroxylase gene. As shown in FIG. 7, a 1.9 kb promoter region of the human genomic clone HG7a26 from -1879 to +24, which is equivalent to nucleotides 2236 through 4139 of FIGS. 4A-4F, was obtained by PCR amplification. A Kpn 1 site was introduced at the 5' end using an HLU-1 primer (HLU-1 primer=5'TACCGCTCGAGTGATTAGAAAGGGAAGGAT 3') (SEQ ID NO:6) and an Xho 1 site was introduced at the 3' end using an HLU-2 primer (HLU-2 primer=5'CAAGAATGATAGATAAAAT 3') (SEQ ID NO:7). This recombinant Kpn 1-Xho 1 fragment containing the human cholesterol 7α-hydroxylase promoter region was ligated into the luciferase vector pGL2-Basic (Promega), which had been cut with restriction enzymes Kpn 1 and Xho. The resulting promoter-luciferase reporter chimeric construct was purified and used to transform host cells, such as the E. coli strain JM101.

The entire 1.9 kb human cholesterol 7α-hydroxylase promoter region and luciferase reporter gene, including a poly(A) signal, is flanked by unique Kpn 1 and BamH 1 restriction enzymes sites. The Kpn 1 and BamH1 fragment is 4.6 kb and is used for microinjection into fertilized oocytes in the production of transgenic animals. Transgenic animals containing this construct, as assayed by Southern Blot analysis, are then tested for various agents which are capable of upregulating or downregulating the CYP7 cis acting elements. Alternatively, given the DNA sequence of the present invention, one of skill in the art is able to contruct various combinations of cis-acting regulatory elements of the human cholesterol 7α-hydroxylase gene to test the specific regions and positional affects that are required for expression of the human cholesterol 7α-hydroxylase gene at levels equivalent to or higher than that in the unmodified organ. The cis-acting regulatory elements of the human cholesterol 7α-hydroxylase gene to be used in such constructs are selected from: the 5' upstream region, the first intron, second intron and third intron of the human gene.

Tissue samples, including liver, are tested for luciferase activity by methods well known in the art. Promega Notes 28: 1 (1990); Promega Technical Bulletin (Promega Corporation, September 1993); Wood, BIOILLUMINESCENCE AND CHEMILUMINESCENCE (John Wiley and Sons, 1991). Briefly, the homogenized tissue supernatants are mixed with luciferin and Coenzyme A in a buffer containing ATP. Luciferin illuminescence, as detected using a luminometer, only occurs in the presence of the recombinant luciferase expressed in the transgenic tissue.

EXAMPLE 3 Production & Analysis of Transgenic Mice Containing DNA Encoding Human Genomic Cholesterol 7A-Hydroxylase

The recombinant CYP7 minigene present in the pH7aMG vector is incorporated into the germ cells of mice as follows: The construction of the pH7aMG shown diagrammatically in FIG. 2. The entire 7.2 kb insert in pH7aMG can be removed by restriction enzyme cleavage with BamH 1 and Kpn 1. The CYP7 minigene DNA was prepared for injection by digestion with 4 units each of BamH1 and Kpn1 per ug of DNA per 1 hour at 37° C., electrophoresed through a 1% agarose gel, and purified as described by Sinn et al., Cell 49: 465 (1987). The isolated 7.2 kb DNA fragment was injected into the pronuclei of fertilized one-cell mouse or hamster eggs derived from the FVB/NHd inbred strain (Taconic laboratory, Germantown, N.J.). About 100 to 1000 copies of linearized plasmid is incorporated per pronucleus. Following microinjection, viable eggs are transferred to the oviducts of pseudopregnant Swiss Webster mice (Taconic Farms), as described by Wagner et al., Proc. Natl. Acad. Sci. USA 78: 5016 91981). Mice are housed in an environmentally controlled facility maintained on a 10 hour dark: 14 hour light cycle. The eggs in the foster females are allowed to develop to term.

Between two and six weeks of age, the DNA of each pup born is analyzed by Southern hybridization using DNA taken from the pup's tail. DNA is extracted from 1.5 cm tail sections. Davis et al. Meth. Enzym. 65: 405 (1980). The nucleic acid pellet is resuspended in 200 μl of 10 mM Tris-Cl pH 7.4, 0.1 mM EDTA, and 10 μg is digested with Kpn1 and BamH1, electrophoresed through 1.0% agarose, and transferred to nitrocellulose. Southern, J. Mol. Biol. 98: 503 (1975). Filters are hybridized overnight to CYP7 transgene specific probe in the presence of 10% dextran sulfate and washed twice in 2× SSC, 0.1% SDS at 64° C. A CYP7 transgene specific probe is a fragment of the CYP7 minigene that will not hybridize to related sequences in the host genome. This fragment is free of repetitive sequences. The CYP7 transgene specific probe is labeled with ³² P dCTP by nick translation. Rigby et al., J. Mol. Biol. 113: 237 (1977).

Southern hybridization indicates which founder mice retain the CYP7 minigene construct.

3.1 Transcription of the Human Cholesterol 7α-hydroxylase Minigene in Transgenic Mice

Transcription of the newly acquired gene in tissues was determined by extracting RNA from the tissues and assaying the RMA by Northern Blot analysis. The excised tissue is rinsed in 5.0 ml cold Hank's buffered saline and total RNA is isolated by methods employing a CsCl gradient. Chirgwin et al. Biochem. 18: 5294 (1979). RNA pellets are washed twice by reprecipitation in ethanol and quantitated by absorbance at 260 nm. Single stranded, uniformly labeled RMA probe is prepared using a transgene specific probe. Such a transgene specific probe is a fragment of the CYP7 minigene that will not hybridize to related sequences in the host genome. This fragment is free of repetitive sequences. Since the human cholesterol 7α-hydroxylase mRNA is 3 kb and the endogenous mouse cholesterol 7α-hydroxylasem RNA is 4 kb, even the entire CYP7 minigene construct cut out of the pH71MG could be used to identify the presence of the transcribed exogenous human cholesterol 7α-hydroxylase gene. Melton et al., Nucl. Acids Res. 12: 7035 (1984).

To test for transcription of the CYP7 minigene, labelled single-stranded probe fragments are isolated on 8M urea 5% acrylamide gels, electroeluted and hybridized to total RNA. Berk et al., Cell 12: 721 (1977). The hybridization mixture contains 50,000 CPM to 100,000 cpm of probe (Specific Activity--10⁸ cpm/ug), 10 μg total cellular RNA, 50% formamide, 500 mM NaCl, 20 mM Tris pH 7.5, 1 mM EDTA. Melton et al. (1984) supra. Hybridization temperatures vary according to the GC content. The hybridizations are terminated by the addition of 1500 units of RNAase A and RNAase T₁ (Sigma, St. Louis, Mo.). RNAase digestions are carried out at 37° C. for 15 minutes. The samples are then ethanol precipitated and electrophoresed on 8M urea 5% acrylamide gels.

The tissues analyzed are liver, muscle, pancreas, stomach, brain, intestines, eye, aorta, salivary gland and kidney. 10 μg of total RNA from each of these tissues is analyzed using a transgene specific probe.

In situ hybridization, using the transgene specific probe, of the histologic sites that transcribe the CYP7 minigene confirm the presence of the exogenous cholesterol 7α-hydroxylase gene in the transcribing tissues.

3.2 Localization of Transgene Expression

mRNA transcripts are evaluated in liver RNA (prepared as above) after conversion to cDNA, PCR amplification and Southern hybridization analysis. Rosenfeld et al., supra. To ensure that CYP7 transgene is specifically evaluated and that the 5' and 3' portion of mRNA transcripts are present, two separate primer pairs are used: a 5' primer pair to detect the 5' end of recombinant construct mRNA transcripts and a CYP7-specific antisense primer, and a 3' primer pair to evaluate the 3' end of the recombinant mRNA transcript. Fiers et al., Nature 273: 113 (1978)

PCR amplification products are evaluated by agarose gel electrophoresis followed by Southern hybridization using ³² P-labeled human CYP7 probes.

Northern analysis of liver RNA from transgenic animals will exhibit CYP7 directed human mRNA transcripts of a size similar to that directed by these constructs in cultured cells. Levels of a constituitively expressed protein transcripts, such as Beta-actin or glyceraldehyde-3-phosphate dehydrogenase, serve as a positive control and are normally similar for both transgenic and nontransgenic tissue samples.

3.3 Expression of Recombinant Human Cholesterol 7α-hydroxylase in Transgenic Animal Tissues

Expression of the human cholesterol 7α-hydroxylase transgene is evaluated by Western Blotting or immunohistochemistry. Alternatively, expression of a linked reporter gene, such as luciferase or LAC-Z, may be used to quantitate the tissues or cells expressing the transgene. For western blot or immunohistochemical detection of transgenically expressed protein, antibodies specific for human cholesterol 7α-hydroxylase are used to detect the presence of this enzyme in various tissue sections or protein preparations from various tissues. Antibodies specific for human cholesterol 7α-hydroxylase are described in J. Chiang (Attorney docket 18748/176, U.S. Ser. No. 08/635,510). Briefly, 1 mg purified CYP7 enzyme is mixed with an equal volume of Freund's adjuvant and 5 mg/ml of heat-killed microbacteria. The emulsified antigen mixtures were injected on the back of New Zealand white rabbits by intradermal injections on multiple sites. After six weeks, 0.5 mg of purified human enzyme was mixed with incomplete adjuvant and used for booster injections to the same rabbits. Six weeks later, blood samples were collected from ear veins and tested for the presence of antibodies by Ouchterlony double diffusion and by immunoblotting as described previously by Chiang, et al., J. Biol. Chem. 265, 3889-3897 (1990), incorporated by reference in its entirety. For immunoblot analysis, one μg of purified human CYP7 enzyme was loaded on a 7.5% SDS-polyacrylamide gel, separated polypeptides were electrophoretically transferred to an Immobilon P membrane by a modified procedure reported previously (Chiang et al., supra. (1990)). Diluted antisera were reacted with membrane and subsequently reacted with second antibody, anti-rabbit IgG conjugated with alkaline phosphatase, and then stained with nitroblue tetrazolium (NBT) and 5-bromo-4-chloro-3-indolylphosphate (DCIP) as described previously.

The presence of human 7 alpha-hydroxylase expression in tissues is evaluated by immunohistochemistry using a human 7 alpha-hydroxylase specific antibody. The alkaline phosphatase monoclonal anti-alkaline phosphatase method is used to detect binding of the specific antibody to various tissue sections.

EXAMPLE 4 Animal Testing

Transgenic animals of the invention are most useful as animal models for testing agents and procedures that promote or inhibit overexpression or under expression of CYP7. The CYP7 expressing animals are tested for materials that are suspected of promoting or inhibiting hypercholesterolemia. The animals are exposed to various dosages of a known agent and tested for peripheral blood cholesterol and bile acid production. Animals and their descendants that have either increased or decreased peripheral blood cholesterol levels are then tested for the effect of an agent on the expression of CYP7.

Transgenic animals treated with agents that cause overexpression of CYP7 are used to study whether such overexpression prevents hypercholesterolemia when such treated animals are on a high cholesterol diet. Also, transgenic mice fed a diet containing high levels of both bile acids and cholesterol are used to determine whether a high bile acid diet suppresses 7α-hydroxylase and thus induces hypercholesterolemia.

EXAMPLE 5 Tissue Culture of Transgenic Cell Lines

The transgenic animals of the invention can be used as a source of cells for cell culture. Cells of the tissues of the transgenic animal that contain the activated recombinant gene can be cultures, using standard tissue culture techniques and used, for example to study the causes of hypercholesterolemia at the cellular and tissue level.

EXAMPLE 6 Production of Transformed Cells: Promoter/Reporter Gene Constructs

Assessment of gene regulation in transformed mammalian cells using the luciferase reporter system is well known to those of skill in the art. deWet et al., Mol. Cell. Biol. 7: 725 (1987). The same pGL2-Basic luciferase vector (Promega) constructs described for the transgenic animals may be used in vitro. Also, luciferase activity in cell culture is performed by methods well known in the art. Promega Notes 28: 1 (1990); Promega Technical Bulletin (Promega Corporation, September 1993). Briefly, the supernatants of lysed cells are mixed with luciferin and Coenzyme A in a buffer containing ATP. Luciferin illuminescence, as detected using a luminometer, only occurs in the presence of the recombinant luciferase expressed in the transformed cells.

The transformed promoter-reporter cells of the invention can be used as models to test for agents that potentially effect the expression of human cholesterol 7α-hydroxylase.

To determine the promoter sequences responsible for regulation of cholesterol 7α-hydroxylase, deletions of the human CYP7 cis-acting elements are ligated upstream of the luciferase reporter gene (Luc). The promoter fragments were generated by the polymerase chain reaction using the primers and a human CYP7 genomic clone as the template. The fragments were blunted by filling in with the Klenow fragment of DNA polymerase and then digested with Xho I. The fragments were then ligated into pGL2-basic vector (Promega) which had been digested with SmaI and Xho I, and transformed into E. coli HB101 cells. The resulting plasmids could be used to transfect primary hepatocytes or hepatoma cells for the study of human luciferase gene expression under the control of the human CYP7 promoter.

Chloramphenicol acetyltransferase (CAT) reporter gene constructs were made by using the polymerase chain reaction and primers to amplify the 5' flanking regions and introns 1, 2 and 3 of the human CYP7 gene. Fragments are ligated into a promoterless pCAT basic vector (Promega). This plasmid is then used to generate nested deletions containing various pieces of 5' flanking DNA, intron 1, intron 2 and/or intron 3.

EXAMPLE 7 Production of Transformed Cells: Minigene Constructs

The DNA of each transformed cell line from each construct is analyzed by Southern hybridization. DNA is extracted from the cells culture and the nucleic acid pellet is resuspended in 200 ul of 10mM Tris-Cl pH 7.4, 0.1 mM EDTA, and 10 ug is digested with Kpnl and BamH1, electrophoresed through 1.0% agarose, and transferred to nitrocellulose. Southern, J. Mol. Biol. 98: 503 91975). Filters are hybridized overnight to CYP7 transgene specific probe in the presence of 10% dextran sulfate and washed twice in 2× SSC, 0.1% SDS at 64° C. A CYP7 transgene specific probe is a fragment of the CYP7 minigene that will not hybridize to related sequences in the host genome. This fragment is free of repetitive sequences. The CYP7 transgene specific probe is labeled with ³² P dCTP by nick translation. Rigby et al., J. Mol. Biol. 113: 237 (1977). Southern hybridization indicates cell lines contain the CYP7 minigene construct.

Transcription of the newly acquired gene in cultured cells is determined by extracting RNA from the cells and assaying the RNA by Northern Blot analysis, as described above.

Expression of recombinant human cholesterol 7α-hydroxylase in cell culture is evaluated by Western Blotting or immunocytochemistry. Alternatively, expression of a linked reporter gene, such as luciferase or LAC-Z, may be used to quantitate the tissues or cells expressing the transgene. For western blot or immunocytochemical detection of the recombinant protein, antibodies specific for human cholesterol 7α-hydroxylase are used to detect the presence of this enzyme in the various transformed cells.

In Vitro Agent Testing

Transformed cell lines of the invention are most useful as in vitro models for testing agents and procedures that promote or inhibit overexpression or under expression of CYP7. The CYP7 expressing cell lines are tested for materials that are suspected of promoting or inhibiting hypercholesterolemia. The cells are exposed to various dosages of a known agent and tested for the presence of human cholesterol 7α-hydroxylase.

EXAMPLE 8 Production and Expression of Truncated Human Cholesterol 7α-Hydroxylase in E. coli

Two primers were designed for the generation of a truncated human cholesterol 7α-hydroxylase cDNA by polymerase chain reaction using the full length human clone PHC7F as the template. Karam and Chiang, Biochem. Biophys. Res. Commun. 185: 588-95 (1992). The 5'-primer had a sequence of 5'GCCATGGCCAGGAGAAGGCAAACGGGT-3, which encoded an N-terminus with a sequence (SEQ ID NO:1) of Met-Ala-Arg(25)-Arg(26)-Arg(27)-Glu(28), etc. The 3'-primer had a sequence (SEQ ID NO:2) of GCCATGGCCGTAATATCATCTAG-3,' which was complementary to the cDNA sequence (SEQ ID NO:3) from 1599 to 1612 near the 3'-end of the coding region. The cDNA generated was sequenced to confirm the human sequence (FIG. 8). This cDNA was ligated to the Nco I site (GCCATG) of the pJL plasmid. The recombinant construct, pJL/H7α1.5 (FIG. 9), was then transformed into a battery of bacteria strains.

It was found that the TOPP3 strain of E. coli harboring pJL/H7 α 1.5 was capable of expressing truncated human cholesterol 7α-hydroxylase in very high amounts. Bacteria carrying pJL/H7α1.5 were cultured in "Terrific" broth containing 100 μg/ml ampicillin for 6 hours. One (1) mM IPTG was added to induce the production of protein at 30° C. for 15 to 18 hours. Addition of 2 mM δ-aminolevulinic acid in the culture increased the expression level by 100%. About 20 nmol of human cholesterol 7α-hydroxylase were expressed per liter of culture.

EXAMPLE 9 Purification of the Bacterially Expressed Human Cholesterol 7α-Hydroxylases

Culturing the bacteria carrying the recombinant vector encoding truncated human CYP7 was performed by inoculating 8 liters of Terrific broth containing 100 μg/ml ampicillin with a 6-hour culture of TOPP3-pJL/H7α1.5. This culture was grown at 37° C. until the O.D.₆₀₀ reached from about 0.4 to about 0.6, which occurred in about 3 hours. IPTG was added to a final concentration of 1 mM and incubation was carried out at 30° C. for 15 to 18 hours.

After induction, the cultures were harvested by centrifugation at 5,000 rpm for ten minutes at 4° C. The cells were then resuspended in 1/100 volume of buffer A (100 mM potassium phosphate, pH 7.4, 0.5% sodium cholate, 20% glycerol, 0.1 mM EDTA, 0.1 mM DTT and 0.5 mM PMSF). The cells were then lysed in buffer A with 200 μg/ml lysozyme. The supernatant was collected after spinning down the total lysate at 100,000× g for one (1) hour at 4° C. The pellet was resuspended thoroughly in the same buffer and centrifuged again. Both supernatants were combined and stored on ice overnight after the addition of 100 units of DNaseI. The clear lysate was then applied to an Octylamino Sepharose 4B column (2.6×15 cm). This column was washed and eluted with the same buffer. The eluted fractions were dialyzed against buffer B (10 mM potassium phosphate, pH 7.4, 0.2% sodium cholate, 0.2% Emulgen 911, 0.1 mM EDTA, 0.05 mM DTT, 0.5 mM phenyl methyl sufonyl fluoride (PMSF)), applied to a hydroxyapatite column (2.4×7 cm) and equilibrated with the same buffer. This column was then washed with 200 ml of 10 mM potassium phosphate buffer, then with 150 ml of 50 mM potassium phosphate buffer and then eluted with 300 ml of 100 mM potassium phosphate buffer. These three buffers also contained 20% glycerol, 0.3% sodium cholate, 0.05 mM EDTA, 0.1 mM DTT and 0.5 mM PMSF. The purified sample was brought to 0.2% Emulgen 911 and then dialyzed against 10 mM potassium phosphate buffer, pH 7.4, 20% glycerol, 0.1 mM EDTA, 0.1 mM DTT, 0.5 mM PMSF and 0.2% Emulgen 911 (buffer C). The sample was then applied to a second hydroxylapatite column (0.5×3.0 cm) equilibrated with buffer C and eluted with buffer C but containing 360 mM potassium phosphate. At this stage, the purity of the human cholesterol 7α-hydroxylase was confirmed by SDS-polyacrylamide gel electrophoresis.

EXAMPLE 10 Characterization of the Purified Human Cholesterol 7α-Hydroxylase

The truncated enzyme was purified from recombinant bacteria. Purification methodology is described by Li and Chiang, J. Biol. Chem. 266 (29): 19186 (1991), the contents of which are expressly incorporated by reference herein in its entirety. The activity of CYP7, in both the presence and absence of the compound, is measured as described by Chiang, Meth. Enzym. 206: 483 (1991), the contents of which is expressly incorporated by reference herein in its entirety.

Purified truncated enzyme was active in the reconstitution of cholesterol 7α-hydroxylase activity in the presence of NADPH-cytochrome P450 reductase and phospholipid (purified CYP7 enzyme (0.1 nmoles), 2 units of NADPH-cytochrome P450 reductase, 40 μg/ml of L-dilauroyl-glyceryl-3-phosphorylcholine, 100 μM cholesterol in 10 μl of 45% Molecusol, 0.015% CHAPS (3-((3-cholamidopropyl) dimethylaminio)-1-propanesulfonate), 0.1M potassium phosphate, pH 7.4, 1 mM EDTA, 5 mM DTT and 0.1% Emulgen 911). The addition of Molecusol, at varying concentrations, stimulated activity by three-fold. The reaction was started by the addition of 1 mM NADPH and proceeded for 20 minutes, at 37° C. Reactions were terminated by adding 0.8% sodium cholate. Products were oxidized by adding 1 unit of cholesterol oxidase and incubated at 37° C. for 10 minutes. The reaction mixture was extracted three (3) times with 6 ml each of petroleum ether and combined extracts were dissolved in 100 μl of acetonitrile: methanol (70:30; v/v) and analyzed on a C18 reverse-phase HPLC column as described previously. Chiang, Meth. in Enzymol. 206: 483-91 (1991).

The K_(m) and V_(max) for cholesterol have been determined in comparison with the truncated, bacterially expressed rat CYP7 enzyme (FIG. 10). The K_(m) for the truncated human enzyme was 5.85 μM and V_(max) was 0.13 nmol/min, which were similar to those of the truncated, bacterially expressed rat enzyme and of intact enzyme isolated from rat liver microsomes. Thus, the isolated truncated human CYP7 enzyme has similar kinetic properties to the truncated rat CYP7 enzyme.

EXAMPLE 11 Assay for Screening Compounds for Ability to Inhibit or Stimulate Non-Truncated CYP7 Enzyme Activity in Human Liver

A. Preparation of Antibodies Against the Purified Human Cholesterol 7α-Hydroxylase

As mentioned above, an assay system using antibodies raised against purified, truncated human CYP7 is used to screen compounds for their ability to inhibit or stimulate non-truncated CYP7 enzyme activity in human liver. Antibodies to truncated human CYP7 can be produced as follows.

One (1) mg purified truncated CYP7 enzyme was mixed with an equal volume of Freund's adjuvant and 5 mg/ml of heat-killed microbacteria. The emulsified antigen mixtures were injected on the back of New Zealand white rabbits by intradermal injections on multiple sites. After six (6) weeks, 0.5 mg of purified human enzyme was mixed with incomplete adjuvant and used for booster injections to the same rabbits. Six (6) weeks later, blood samples were collected from ear veins and tested for the presence of antibodies by Ouchterlony double diffusion and by immunoblotting as described previously by Chiang et al., J. Biol. Chem. 265: 3889-97 (1990), incorporated by reference in its entirety.

For a Western Blot analysis, one (1) μg of purified human CYP7 enzyme was loaded on a 7.5% SDS-polyacrylamide gel, separated polypeptides were electrophoretically transferred to an Immobilon P membrane by a modified procedure reported previously. Chiang et al., supra. (1990). Diluted antisera were reacted with membrane and subsequently reacted with second antibody, anti-rabbit IgG conjugated with alkaline phosphatase, and then stained with nitroblue tetrazolium (NBT) and 5-bromo-4-chloro-3-indolylphosphate (DCIP) as described previously.

B. Assay Using Antibodies Against the Purified Human Cholesterol 7α-Hydroxylase

The specific antibody described above can be used in a screen assay to measure the inhibitory or stimulatory effects of a particular compound on the expression of CYP7 in human liver by a corresponding analysis of the effect on truncated CYP7. To quantitate the amount of expressed truncated enzyme in Western Blot analysis, such as described immediately above, varying concentrations of purified truncated human CYP7 enzyme, from 1 to 10 μgs, are run on adjacent lanes on the 7.5% SDS-polyacrylamide gel to those lanes containing the human CYP7 enzyme from the experimentally treated cells. A stimulation of truncated CYP7 expression is detected by a darker band, relative to control, on the Western blot. If a compound stimulates CYP7 enzyme expression and/or activity, then such an agent or drug could potentially be used to reduce cholesterol in humans. If an agent or drug inhibits CYP7 enzyme expression and/or activity, then such a compound should be used with caution because it potentially could increase serum cholesterol levels in humans.

    __________________________________________________________________________     SEQUENCE LISTING                                                               (1) GENERAL INFORMATION:                                                       (iii) NUMBER OF SEQUENCES: 11                                                  (2) INFORMATION FOR SEQ ID NO:1:                                               (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 27 base pairs                                                      (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: single                                                       (D) TOPOLOGY: linear                                                           (xi) SEQUENCE DESCRIPTION: SEQ ID NO:1:                                        GCCATGGCCAGGAGAAGGCAAACGGGT27                                                  (2) INFORMATION FOR SEQ ID NO:2:                                               (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 6 amino acids                                                      (B) TYPE: amino acid                                                           (D) TOPOLOGY: linear                                                           (xi) SEQUENCE DESCRIPTION: SEQ ID NO:2:                                        MetAlaArgArgArgGlu                                                             15                                                                             (2) INFORMATION FOR SEQ ID NO:3:                                               (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 23 base pairs                                                      (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: single                                                       (D) TOPOLOGY: linear                                                           (xi) SEQUENCE DESCRIPTION: SEQ ID NO:3:                                        GCCATGGCCGTAATATCATCTAG23                                                      (2) INFORMATION FOR SEQ ID NO:4:                                               (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 1524 base pairs                                                    (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: double                                                       (D) TOPOLOGY: linear                                                           (xi) SEQUENCE DESCRIPTION: SEQ ID NO:4:                                        AGTTTAACTTTAGTAAGGAGTCTAGACCATGGCCAGGAGAAGGCAAACGGGTGAACCACC60                 TCTAGAGAATGGATTAATTCCATACCTGGGCTGTGCTCTGCAATTTGGTGCCAATCCTCT120                TGAGTTCCTCAGAGCAAATCAAAGGAAACATGGTCATGTTTTTACCTGCAAACTAATGGG180                AAAATATGTCCATTTCATCACAAATCCCTTGTCATACCATAAGGTGTTGTGCCACGGAAA240                ATATTTTGATTGGAAAAAATTTCACTTTGCTACTTCTGCGAAGGCATTTGGGCACAGAAG300                CATTGACCCGATGGATGGAAATACCACTGAAAACATAAACGACACTTTCATCAAAACCCT360                GCAGGGCCATGCCTTGAATTCCCTCACGGAAAGCATGATGGAAAACCTCCAACGTATCAT420                GAGACCTCCAGTCTCCTCTAACTCAAAGACCGCTGCCTGGGTGACAGAAGGGATGTATTC480                TTTCTGCTACCGAGTGATGTTTGAAGCTGGGTATTTAACTATCTTTGGCAGAGATCTTAC540                AAGGCGGGACACACAGAAAGCACATATTCTAAACAATCTTGACAACTTCAAGCAATTCGA600                CAAAGTCTTTCCAGCCCTGGTAGCAGGCCTCCCCATTCACATGTTCAGGACTGCGCACAA660                TGCCCGGGAGAAACTGGCAGAGAGCTTGAGGCACGAGAACCTCCAAAAGAGGGAAAGCAT720                CTCAGAACTGATCAGCCTGCGCATGTTTCTCAATGACACTTTGTCCACCTTTGATGATCT780                GGAGAAGGCCAAGACACACCTCGTGGTCCTCTGGGCATCGCAAGCAAACACCATTCCAGC840                GACTTTCTGGAGTTTATTTCAAATGATTAGGAACCCAGAAGCAATGAAAGCAGCTACTGA900                AGAAGTGAAAAGAACATTAGAGAATGCTGGTCAAAAAGTCAGCTTGGAAGGCAATCCTAT960                TTGTTTGAGTCAAGCAGAACTGAATGACCTGCCAGTATTAGATAGTATAATCAAGGAATC1020               GCTGAGGCTTTCCAGTGCCTCCCTCAACATCCGGACAGCTAAGGAGGATTTCACTTTGCA1080               CCTTGAGGACGGTTCCTACAACATCCGAAAAGATGACATCATAGCTCTTTACCCACAGTT1140               AATGCACTTAGATCCAGAAATCTACCCAGACCCTTTGACTTTTAAATATGATAGGTATCT1200               TGATGAAAACGGGAAGACAAAGACTACCTTCTATTGTAATGGACTCAAGTTAAAGTATTA1260               CTACATGCCCTTTGGATCGGGAGCTACAATATGTCCTGGAAGATTGTTCGCTATCCACGA1320               AATCAAGCAATTTTTGATTCTGATGCTTTCTTATTTTGAATTGGAGCTTATAGAGGGCCA1380               AGCTAAATGTCCACCTTTGGACCAGTCCCGGGCAGGCTTGGGCATTTTGCCGCCATTGAA1440               TGATATTGAATTTAAATATAAATTCAAGCATTTGTGAATACATGGCTGGAATAAGAGGAC1500               ACTAGATGATATTACGGCCATGGC1524                                                   (2) INFORMATION FOR SEQ ID NO:5:                                               (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 482 amino acids                                                    (B) TYPE: amino acid                                                           (D) TOPOLOGY: linear                                                           (xi) SEQUENCE DESCRIPTION: SEQ ID NO:5:                                        MetAlaArgArgArgGlnThrGlyGluProProLeuGluAsnGlyLeu                               151015                                                                         IleProTyrLeuGlyCysAlaLeuGlnPheGlyAlaAsnProLeuGlu                               202530                                                                         PheLeuArgAlaAsnGlnArgLysHisGlyHisValPheThrCysLys                               354045                                                                         LeuMetGlyLysTyrValHisPheIleThrAsnProLeuSerTyrHis                               505560                                                                         LysValLeuCysHisGlyLysTyrPheAspTrpLysLysPheHisPhe                               65707580                                                                       AlaThrSerAlaLysAlaPheGlyHisArgSerIleAspProMetAsp                               859095                                                                         GlyAsnThrThrGluAsnIleAsnAspThrPheIleLysThrLeuGln                               100105110                                                                      GlyHisAlaLeuAsnSerLeuThrGluSerMetMetGluAsnLeuGln                               115120125                                                                      ArgIleMetArgProProValSerSerAsnSerLysThrAlaAlaTrp                               130135140                                                                      ValThrGluGlyMetTyrSerPheCysTyrArgValMetPheGluAla                               145150155160                                                                   GlyTyrLeuThrIlePheGlyArgAspLeuThrArgArgAspThrGln                               165170175                                                                      LysAlaHisIleLeuAsnAsnLeuAspAsnPheLysGlnPheAspLys                               180185190                                                                      ValPheProAlaLeuValAlaGlyLeuProIleHisMetPheArgThr                               195200205                                                                      AlaHisAsnAlaArgGluLysLeuAlaGluSerLeuArgHisGluAsn                               210215220                                                                      LeuGlnLysArgGluSerIleSerGluLeuIleSerLeuArgMetPhe                               225230235240                                                                   LeuAsnAspThrLeuSerThrPheAspAspLeuGluLysAlaLysThr                               245250255                                                                      HisLeuValValLeuTrpAlaSerGlnAlaAsnThrIleProAlaThr                               260265270                                                                      PheTrpSerLeuPheGlnMetIleArgAsnProGluAlaMetLysAla                               275280285                                                                      AlaThrGluGluValLysArgThrLeuGluAsnAlaGlyGlnLysVal                               290295300                                                                      SerLeuGluGlyAsnProIleCysLeuSerGlnAlaGluLeuAsnAsp                               305310315320                                                                   LeuProValLeuAspSerIleIleLysGluSerLeuArgLeuSerSer                               325330335                                                                      AlaSerLeuAsnIleArgThrAlaLysGluAspPheThrLeuHisLeu                               340345350                                                                      GluAspGlySerTyrAsnIleArgLysAspAspIleIleAlaLeuTyr                               355360365                                                                      ProGlnLeuMetHisLeuAspProGluIleTyrProAspProLeuThr                               370375380                                                                      PheLysTyrAspArgTyrLeuAspGluAsnGlyLysThrLysThrThr                               385390395400                                                                   PheTyrCysAsnGlyLeuLysLeuLysTyrTyrTyrMetProPheGly                               405410415                                                                      SerGlyAlaThrIleCysProGlyArgLeuPheAlaIleHisGluIle                               420425430                                                                      LysGlnPheLeuIleLeuMetLeuSerTyrPheGluLeuGluLeuIle                               435440445                                                                      GluGlyGlnAlaLysCysProProLeuAspGlnSerArgAlaGlyLeu                               450455460                                                                      GlyIleLeuProProLeuAsnAspIleGluPheLysTyrLysPheLys                               465470475480                                                                   HisLeu                                                                         (2) INFORMATION FOR SEQ ID NO:6:                                               (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 30 base pairs                                                      (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: single                                                       (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: DNA (genomic)                                              (xi) SEQUENCE DESCRIPTION: SEQ ID NO:6:                                        TACCGCTCGAGTGATTAGAAAGGGAAGGAT30                                               (2) INFORMATION FOR SEQ ID NO:7:                                               (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 19 base pairs                                                      (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: single                                                       (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: DNA (genomic)                                              (xi) SEQUENCE DESCRIPTION: SEQ ID NO:7:                                        CAAGAATGATAGATAAAAT19                                                          (2) INFORMATION FOR SEQ ID NO:8:                                               (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 504 amino acids                                                    (B) TYPE: amino acid                                                           (C) STRANDEDNESS: single                                                       (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: peptide                                                    (xi) SEQUENCE DESCRIPTION: SEQ ID NO:8:                                        MetMetThrThrSerLeuIleTrpGlyIleAlaIleAlaAlaCysCys                               151015                                                                         CysLeuTrpLeuIleLeuGlyIleArgArgArgGlnThrGlyGluPro                               202530                                                                         ProLeuGluAsnGlyLeuIleProTyrLeuGlyCysAlaLeuGlnPhe                               354045                                                                         GlyAlaAsnProLeuGluPheLeuArgAlaAsnGlnArgLysHisGly                               505560                                                                         HisValPheThrCysLysLeuMetGlyLysTyrValHisPheIleThr                               65707580                                                                       AsnProLeuSerTyrHisLysValLeuCysHisGlyLysTyrPheAsp                               859095                                                                         TrpLysLysPheHisPheAlaThrSerAlaLysAlaPheGlyHisArg                               100105110                                                                      SerIleAspProMetAspGlyAsnThrThrGluAsnIleAsnAspThr                               115120125                                                                      PheIleLysThrLeuGlnGlyHisAlaLeuAsnSerLeuThrGluSer                               130135140                                                                      MetMetGluAsnLeuGlnArgIleMetArgProProValSerSerAsn                               145150155160                                                                   SerLysThrAlaAlaTrpValThrGluGlyMetTyrSerPheCysTyr                               165170175                                                                      ArgValMetPheGluAlaGlyTyrLeuThrIlePheGlyArgAspLeu                               180185190                                                                      ThrArgArgAspThrGlnLysAlaHisIleLeuAsnAsnLeuAspAsn                               195200205                                                                      PheLysGlnPheAspLysValPheProAlaLeuValAlaGlyLeuPro                               210215220                                                                      IleHisMetPheArgThrAlaHisAsnAlaArgGluLysLeuAlaGlu                               225230235240                                                                   SerLeuArgHisGluAsnLeuGlnLysArgGluSerIleSerGluLeu                               245250255                                                                      IleSerLeuArgMetPheLeuAsnAspThrLeuSerThrPheAspAsp                               260265270                                                                      LeuGluLysAlaLysThrHisLeuValValLeuTrpAlaSerGlnAla                               275280285                                                                      AsnThrIleProAlaThrPheTrpSerLeuPheGlnMetIleArgAsn                               290295300                                                                      ProGluAlaMetLysAlaAlaThrGluGluValLysArgThrLeuGlu                               305310315320                                                                   AsnAlaGlyGlnLysValSerLeuGluGlyAsnProIleCysLeuSer                               325330335                                                                      GlnAlaGluLeuAsnAspLeuProValLeuAspSerIleIleLysGlu                               340345350                                                                      SerLeuArgLeuSerSerAlaSerLeuAsnIleArgThrAlaLysGlu                               355360365                                                                      AspPheThrLeuHisLeuGluAspGlySerTyrAsnIleArgLysAsp                               370375380                                                                      AspIleIleAlaLeuTyrProGlnLeuMetHisLeuAspProGluIle                               385390395400                                                                   TyrProAspProLeuThrPheLysTyrAspArgTyrLeuAspGluAsn                               405410415                                                                      GlyLysThrLysThrThrPheTyrCysAsnGlyLeuLysLeuLysTyr                               420425430                                                                      TyrTyrMetProPheGlySerGlyAlaThrIleCysProGlyArgLeu                               435440445                                                                      PheAlaIleHisGluIleLysGlnPheLeuIleLeuMetLeuSerTyr                               450455460                                                                      PheGluLeuGluLeuIleGluGlyGlnAlaLysCysProProLeuAsp                               465470475480                                                                   GlnSerArgAlaGlyLeuGlyIleLeuProProLeuAsnAspIleGlu                               485490495                                                                      PheLysTyrLysPheLysHisLeu                                                       500                                                                            (2) INFORMATION FOR SEQ ID NO:9:                                               (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 5537 base pairs                                                    (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: single                                                       (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: DNA (genomic)                                              (xi) SEQUENCE DESCRIPTION: SEQ ID NO:9:                                        TTTTTGGTTATCTTTTCAGCCGTGCCCCACTCTACTGGTACCAGTTTACTGTATTAGTCG60                 ATTTTCATGCTGCTGATAAAGACATACCTGAAACTGGACAATTTACAAAAGAAAGAGGTT120                TATTGGACTTACAATTCTACATCACTTGGGAGGCCTCACAATCATGATGGAAGGAGAAAG180                GCACATCTCACATGGCAGCAGACAAGAAAAGAGCTTGTGCAGGGAAACTCCTCTTTTTAA240                AACCATCAGATCTCATGAAATTTATTCATTATCATGACAATAGCACAGGAAAGAACTGCA300                CCCATAATTCAGTCACCTCCTACCAGGTTCCTCCCACAACACGTGAGAATTCAAGATGAG360                ATTTGGATGGGGACACAGCCAAACCATGTCACACTACCATGCCTGACTTCCTTTCCATTT420                TTGTATATTTGCTTGTTCTTCATTTGCCCGAGAAGTAACTCTAAAGGGCTGTATTATTTG480                GATATTAGATTGGCATTTTATCTGACTGGGATATCTTGCTGTGATTGTCCATGTATAAGA540                TCAGCTTTTCTATAAGCCATATTTTTAAAAAGATATATTAATTTTTTAAAAATCCACCTG600                TCTAAATAAATGCACAAAGCCCCCCAAAAACCTAGATTCTAAGAAAAATCTATGTACTGC660                CATACAATGATTGATATTAATATTTATGGTGATAAATTACACACAAAAAATGTGTGATCT720                CTGTTTAAACAGGCAAAAACAAAAAACACATGAAATAAATCTATGGCATCTATAGCCAAA780                ACTGGAAACAACCCACATATCCATCAATAGGAAATCAGTTAAATAAATTATAGTACATTT840                ATCCAATGGAAGATTAAGCACATATTCAATATAATTATTTATACACACATATAGATACAC900                ACATGTATAAATATAGAGAATACTGTGGGTGTATGTGTGTGTGTGTTTATATACATATAT960                ATACACACACAGTACTGTTGCCTACCTTCTTTTGTCTTAATTCTGTGAACTCTCATTCAC1020               TCTGCTTCAGTAGGATACCTCCTTCTTTTTGGTTCTTAGACTCACCAAGTTGATCCTTGA1080               CTCAAGACATTGCATTTGCTGCTTCCTCTTCCTGGAATATCCTTCCTTCTGATATTCACA1140               TGAGTAGTCTCTTCTTGTCATTCAGATCTCAAATGTCACAATTTCAGAGAGCCCATCTCT1200               GATCATCATATCTAAAGTTGTCCTCATTCCCCCATAGCTTTCTATACCATGTTTTATTTT1260               TTTCATAACATGTATTTTATTACTCCTTTCTCCATTGGAATAGAATCTCCATTAGATTAG1320               GAAATCTGCCTATCTTATTAATGCCTGCAACTGGAATACTTTTGAAGAGTTCTTGGCACG1380               TAATAAATACTCAACTAATATTTTTGTGTACACAGAAATAAAGTTTGGAAGAACAGATGC1440               CAAATTGTTACTAGTGGTTACTTCTGAGTAAAGGAGTAGCATGGTAGGTAAATTATTAAT1500               AGATGTTCACTTTCCACCAAGATATGTTTTAGTTAGTCTTAACTTACTTGAAATGAAATT1560               TATTACTTTAATAATTAGAAACATTGATAAACATTTTAGTCACAAGAATGATAGATAAAA1620               TTTTGATGCTTCCAATAAGTTATATTTATCTAGAGGATGCACTTATGTAGAATACTCTCT1680               TGAGGATGTTAGGTGAGTAACATGTTACTATATGTAGTAAAATATCTATGATTTTATAAA1740               AGCACTGAAACATGAAGCAGCAGAAATGTTTTTCCCAGTTCTCTTTCCTCTGAACTTGAT1800               CACCGTCTCTCTGGCAAAGCACCTAAATTAATTCTTCTTTAAAAGTTAACAAGACCAAAT1860               TATAAGCTTGATGAATAACTCATTCTTATCTTTCTTTAAATGATTATAGTTTATGTATTT1920               ATTAGCTATGCCCATCTTAAACAGGTTTATTTGTTCTTTTTACACATACCAAACTCTTAA1980               TATTAGCTGTTGTCCCCAGGTCCGAATGTTAAGTCAACATATATTTGAGAGACCTTCAAC2040               TTATCAAGTATTGCAGGTCTCTGATTGCTTTGGAACCACTTCTGATACCTGTGGACTTAG2100               TTCAAGGCCAGTTACTACCACTTTTTTTTTTCTAATAGAATGAACAAATGGCTAATTGTT2160               TGCTTTGTCAACCAAGCTCAAGTTAATGGATCTGGATACTATGTATATAAAAAGCCTAGC2220               TTGAGTCTCTTTTCAGTGGCATCCTTCCCTTTCTAATCAGAGATTTTCTTCCTCAGAGAT2280               TTTGGCCTAGATTTGCAAAATGATGACCACATCTTTGATTTGGGGGATTGCTATAGCAGC2340               ATGCTGTTGTCTATGGCTTATTCTTGGAATTAGGAGAAGGTAAGTAATGTTTTATCTTTA2400               AATTGCTCTTTGATTCATCCATTTAATTTTTTTACCTTCATTTTTATACAGTAAATTTGG2460               TTTTCTATACTTACACATATTAGCATTATCTTCCTTATGTTTTAAATGAAAAATTTGATT2520               TGAATTTTTAAAGTAATATCTTTTTTACTATATCTCACAAGACATATGACAGCTTCCCTT2580               TTTAGTATTGGCATATACCGATGGTAATATATAAATGTATATTGGTGTTAAACATAACTG2640               ACAGAAATTGTATAAGGTCTCTATGTACATTTATATGTGTATCTAAAGAGGAAGCCCAGA2700               TTAGTAAGGATACAAGTAGCAAGTGGGAATCTACAATGGAAAGGATTGCTTTCTCTCACA2760               TGGCTTCAATAGATACTCTTGCTTAAATAAATGTTCTCTTTTAAGCTCATTCTTGTGCAT2820               CGCATAGACTCAGCCTAAGCCTGAACAAGAGCATAGAGCCTGAGCTGATCATTCTATTAC2880               TGTTTTTAAATAAATGTTAATCAACTGTGGTGAATTGGGAAAGTTTGCTGAGTGTATGTG2940               ACATCGATTTCATTTATTTACAACTGGTTCAAGAATGCAAGAAAAACAAATACAGTCAGA3000               TCCAGAACCATAGTTTATTTAACTTCTAATTGGCTCAAGGAGTAATTGTGGGGAGGCATA3060               TAGATATTCTCTGCTATGTCAATCTCAAAAAGAGAAAATAACCCTAACCATCTTTCAGCT3120               TTGTAGATTGCTATGTGTTTTCTGCCTTTGCAGTTTCTTTCAGGCCTGATAGTTTTTACT3180               TTTAATTAAACTACTTATCTTCAAACTAAGAAAAGAAAGGTAATTACTTTATACTGTATT3240               ATTCTATCAAGAGGTACAGAAGTTTATGTTGGAAAATAAGTTTACATGTTCTAATAAAAA3300               CATTTTAAAGGAGCACTGAATTACAATAGATGATTCCGTCAGTGTTTATCTTACTCAATT3360               TCATTTTATAATAAGCTGATTTCTCACATGAGATTCTTCTTCTCTGAAACCATCCTTATA3420               GAATATAATATAGATATCTTTAAACTAGGAATATTTTCAAAACCTCAGTTCTGAAATCCT3480               CCCTTATTCAGTGATCTGTGTCTTTAAAGAAAATAATCAAAAGAAACATTTTGAGATATT3540               TAGAAAAATGATGCTTAGCAAAGTGATAAACACTAGAATGTAGTTTTGTTTCCGCACTGA3600               CAACAAGAATCTTGTTGGTCTTGTAAATCCTTTTGCCTGTATCACTGGGAAAAGTGATGA3660               GCACATAGTAGACGGGTGCTTGTTGAATGTGTATATGGACGGATGCATGAATGGATGGAT3720               TTAGTAATCCTTTCCACCAACATATCATGTTACTAGGTTAATATAACCTATTACTGTAGT3780               AAAAGAGCAGGGCCCATCCAACAAAAGAAATATCTATAAACTATAGGGTTTCAAAGTTTG3840               AAGTCAGTGGGAAAAATTTTAAAACCTGATGTAAGTAAAAACCCAAAACTGTAATCATCC3900               ATGTCTATCATACACTTGTGTCTGACAGGCAAACGGGTGAACCACCTCTAGAGAATGGAT3960               TAATTCCATACCTGGGCTGTGCTCTGCAATTTGGTGCCAATCCTCTTGAGTTCCTCAGAG4020               CAAATCAAAGGAAACATGGTCATGTTTTTACCTGCAAACTAATGGGAAAATATGTCCATT4080               TCATCACAAATCCCTTGTCATACCATAAGGTGTTGTGCCACGGAAAATATTTTGATTGGA4140               AAAAATTTCACTTTGCTACTTCTGCGAAGGTAAGCAGTTTTACATTTATATACCATTCTG4200               TTTGTCTTCTACCTTTTTATGTGCTTGTCTATTTAGAAATTTTGATGTACTTAGATTTTA4260               TGATAAAGGTGTTGAAGAGAGTTATCCTTATGTGGAGATTCTTAGAAACATAAATAAATT4320               ATACGTAGCTTCTTAGTAATAATCATTTAGAAAGTCAAAATAGGTATAGATTTCCGTCAT4380               TTGCTTTGCACGAGCTAATGAGGGTGAAATACAGATTAAATGCTCTACTGAGACAGGTGG4440               CACTGTACGAATAAGATAGATTAAAATTCATCACATCAGCAATGTCTATGCAGAGCGAAG4500               TGACGGAAACCTAACATTCAGCAGTTGTCTCACCACACTTGTGCCACACAGTGTTTCATT4560               TTGATAAGGAATTGGCAAGATATTTTAACATCATTTAGATGTAATAAAAGAAGATCTGTT4620               ACTGAGAAAAAAAACCAATAACTACTTACTTACTGCAAATAAATATTAGCTTTGGTCTTT4680               GTGACTAAGTAGCTTAAAGTTTGGTTAAAATACATCTACAGCTGGACACAATGGAACACA4740               CCTGTAGTCCCTGCTATTTGAGAGGCTGAGGCAGGAGGATCGCTTGAGTCCAGGAGTTTG4800               AGGCTGCAGTGAGCTATCATTGTGTCACTGCACTCCAGCCTGGGTGACAATGTGAGACCC4860               CATCTCTAAAAGAAAAAGAAAAAGAAATCTACAAATAATATAAAAGATAACTAATGATTT4920               TAAAACATTATCAATTAGTTTATGTGCAATAGCTGTAAATAAGTGCAGTAGCATAAGAAA4980               TAAGACATAGATGACTTGAGTGATCCAGGGGAGTGCCACTGAAGTTGGCTTTAAAGGAAA5040               GGTACAGTTTGGTCATTTATTTGTAAAGTGCTATGAACTTGTACAAGGGAAAGCCAATTT5100               CCCGTGTTTACCAAGTAAGGAACTATGAAAGTATCTAATCCGTTTTTCAGTCATTTACTA5160               TGACTAGGTCAGGTTTAACTTCTTTTTCTGCATGTTTTATTTGCTATCAGGCATTTGGGC5220               ACAGAAGCATTGACCCGATGGATGGAAATACCACTGAAAACATAAACGACACTTTCATCA5280               AAACCCTGCAGGGCCATGCCTTGAATTCCCTCACGGAAAGCATGATGGAAAACCTCCAAC5340               GTATCATGAGACCTCCAGTCTCCTCTAACTCAAAGACCGCTGCCTGGGTGACAGAAGGGA5400               TGTATTCTTTCTGCTACCGAGTGATGTTTGAAGCTGGGTATTTAACTATCTTTGGCAGAG5460               ATCTTACAAGGCGGGACACACAGAAAGCACATATTCTAAACAATCTTGACAACTTCAAGC5520               AATTCGACAAAGTCTTT5537                                                          (2) INFORMATION FOR SEQ ID NO:10:                                              (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 2575 base pairs                                                    (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: single                                                       (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: DNA (genomic)                                              (xi) SEQUENCE DESCRIPTION: SEQ ID NO:10:                                       GAATTCTACTCTTTAAAGGGGTGAATATTATGGTACTTGAATTTTATCTCAAGAAAAATG60                 AATAAAAAGTAACTAAATCATTGAAAATATCTGATGGCATGGGGTTTGTGGGGTAACTGG120                CATTCCACAGTGATTTTCAAAGGGCTTGTGCTGTTTTCATTTTGCTTTGTTTTAGTTATG180                GAGCCCTTCCTTGAAACAAACTTCATACTACAGTCCTCTTTCATGAAGCAGAAGAGGGCA240                GTGGGCAGAGCTCTCCTTTGGCTTTCTCCCCCACCACAACAGGGAGCCCTGGAGCTCTAG300                GAGAGAAAATCTGAAATATAAAGGGCATGCATGTGAGCTGTGGAGTCCCAGAGCCCTGGG360                TTTGCATCCTAGATCTGCAACTCCCGTGAATTGAGTTTTGGGAAGTTGCTGAAACTCTGA420                CCTCCTGTTTTCTCATGGTATTGTTGTAAGGGTTAAATGAGACAATGTATGTGAAGACCC480                TGGCCCCACAGTAGAGGCTCTGCACACATTTCAGCGATACTTTCCTCATGTATTTCCAAA540                AATGTTTTCTCATTTTCTTAAAATGTCAGAAAGAAGACAACAGAACTTACTTGCCTTTTA600                CAACAGAACAAATGGAGCAAGTCAGAGGTCAAGGTGCTAACATTCTTCATGGTTCCTCAC660                CACCTTTTGTTCTGTTAGCCTATAGGGAAAAGTCTTCTTTCTCATCTCATTATCTGCAGG720                GGAAAATAGTACTTCAGCAAGTGATCCAGTTGAAGAACATCTCCAGGGCCATTAACATAC780                AGAGGTTTGTTCTACTCTCTCTGTGCTCCATGTCTAAGAACCTCAGCCTTCCTCCTAGGA840                GCTAGGGAAAGTCAGGAAAGTGAAAATAGTACCCCAGCTAATGAACTGCCCTGTGCTGGC900                CTGAGAAGACAAGACCAGCTTCCTCAATGGCTCAAGATTTGGTTTCCTTCAATATGTCCT960                TTTGGAAATATGTCCATGACATCGGAGAGATAAAAGGAGCCAGGATTGCTCACATTCAGG1020               AAAAAAGCTCCACTATCTTTCTCTCTCTCCCTCTTTCTCTCCCTCCCCCTGACTGCCCTC1080               TTCTCTATCTCTCTCTCTCCCTGAGCTGGCAAGGTTAATTGGTCGCAGAAAGCCGAAGAA1140               ACAAGTGGGCCTCCTGGAACAAAGTTCAAAAAGCCGAAAACGGGAAGAAAACTAACCACA1200               AAAGTAAAGGAACCACTTAGCCTTCTTTGATTCCAGGCCCCCAAGCCTGTCTTTAACTTG1260               GATGAATGGAGTTCTTCCTGTGCTACAGCACCGCATAGTAGGGGCTGCCCTGGGCCTGAA1320               GCCAGAGCTTCACCATATTCAGTCATCTGTACATTGAGGCAACAGTGCCTGCTTCATGGT1380               GCTACCCTGTGGATTAAATGAAGCAAGTTTTTGATGATCTTGACACTGAATATTGATGCA1440               TTGGTCAGACTTTTTCTGATAGTAAAAAATGGTGGTTTCTTGTTGTCAGAAATCAAATCA1500               ATATATTTGTTCTCCTGTTGATTAGCTATGTCCCCTAGAGGGCAGCGACTTTGCCTGTCT1560               TATTTATCTCTGCATCTCCAGCACTTAAAAGGTGCCTTGCATAAGGTACATATTAAGTTC1620               ATATGAATGAATGAATGAAATGCATATGATTTATTCATACCCAGTTGGTGGTGTGTTTAC1680               CCTTTCCTAAACCTGTAGTCAGATGGCCTTTGAATCCCCTGTACTTCTTGTGAGGTACTG1740               TGCTGTAAAGGTGGACTATCACACTTCAGTTCAGAGCAATCTGGGCTTGAATCCTGGATT1800               TGCCAGTTTATTAACTATAGCAAACATTTTTGAGCATACATTGTGCCAAGTGCTAGGCTA1860               ACTGTCTTACACACATTGTCTTATTTCGTCTTAATATCTATGAGTCATGCACTATAATCA1920               TCCCCATTTTACAGATAAGAAAGCAAAGACTTGGAGAGGAAAAGCATCTTGTTCAAAGGT1980               AAATACTTAATGGCCAAGCCAACATGCAAATCTAGATTTAATTGCAGCTTCCTCTTCATC2040               TACCATTCGAACTAATTCAAGCTATGTAATATTTCCCACTGAACCTTCTTGCCTCTACTT2100               CCTCATCTTTAACATGGTCAAAATACCTGTCCTGCCCAAGTTAGTTATTTCATTAAAGTA2160               GAAAAATACAAGAGAAGCTTTTAAAATGTGAAACCTCAAATGAATGTAAAATTATGATGA2220               TTCCTTTAGAATTTGTCAACACCTTCTTTTCTCTACTCCTGCTAGGCATTTACAATCTCA2280               AAACCATGTATTTAAGATGCAAAACTATATTTGTATTTGCCATAACTGGTTTCTTTCCCT2340               ATGGCTTCATGAAAATGTGGCTCGAATGTGTTTATTATGAAAGCCCCAAATTAATCACGA2400               CAAGACTTCACCAGCCCATTCCACAATAGACTCCCATTACTTTGCCCTGACTTAGAAACC2460               TCATATACAGTCTTGATTCAGTACAGCTCTGTGATGCTCTTGGAAAATGCAAAGTGCTTT2520               CTTAATTGAGGCAATCTGTGTCCCACTACAGAGAGGTGGTTTAACTTGTGAATTC2575                    (2) INFORMATION FOR SEQ ID NO:11:                                              (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 2316 base pairs                                                    (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: single                                                       (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: DNA (genomic)                                              (xi) SEQUENCE DESCRIPTION: SEQ ID NO:11:                                       AGAGCAACCTGGGCAACATAGCAAAACCCTGTCTCTGCAAACAATAAAAAGAAGAAAATT60                 AGCTGGGTATGGTGGCACATGCTATAGTCGCAGCTACTCGAGAGGTTGAGGTGGGAGGAT120                CAGTTCAGCCTGGGAGGTTGAGGCTGCAGTGAGCCAGATCATGCCACTGCACTGCAGCAT180                GGGCAACAGAATGAGACCCTGGCTAAAAGAAAACAAAATAAAAAATTCAGACACAGGTTG240                AATCATTGATAACAGCATAGTGGTAACAGAAAGAAAGTTTGGGAAATTTTTATCTGATCA300                GCTTCCCATACCCTGTTCATCTTTGTGTTATGCACTGCCAGGCTGTCTGTAGGTTCAGAC360                TCTATATCATATGACCTTCAAACACTTGGTTTGTTCTTCTCCTTCCTTCCTCCCTTCTTC420                TTTCATTTTTTATCTTTTTTTCTTTTAAAATGTTTAGATAGTATAATAAGGAACTGCTGA480                GGCTTTCCAGTGCCTCCCTCAACATCCGGACAGCTAAGGAGGATTTCACTTTGCACCTTG540                AGGACGGTTCCTACAACATCCGAAAAGATGACATCATAGCTCTTTACCCACAGTTAATGC600                ACTTAGATCCAGAAATCTACCCAGACCCTTTGGTAAAGTCGCAGTGTGCCCGAATTGAAA660                TTCAATATCCAGGTGATAGCTACCTAGATCTAAATAAAGAGGAAATTTACAATGGTAGAA720                TTGATTTTCTCATAGTAGTCACAGGAATTGTCTGACTTAATTGTGTTAAATATTCATATA780                TTTTGGAAAATTTAGATAGTGGTCTGAATTTTTCATTTTAGTCCTGATATTTGCCATCAC840                ACAGTCTTTGCTAGATTATATTTGCAGTCATGATAATAAACCTGCCACTTTTTTTTTCTT900                AAAAAGCACCTCCTCCCAAATCCAGGAAATTGGAGGCTAATATATTGATTATTCTAGTTT960                CTTCTGGGAACCCTTCTCTCTCTAGCTCTGCCTGACTAAGGAACTAATCGTTCAAGCAGG1020               ATAGGAAGGTATCACAAGGCTTCCTTAGCTGCATTAAGCTCCTGTTCCTTATTACTTTCT1080               GATTCAATGTGGAGTATTTGCTAAATCACTAATGGGGTAGAATTAAAAAGAAAATTACTC1140               TTTGGAGCTTCCAGGTTTAGAAAGAGATAAATTTCTTTAAAACTAGCTTAAAGGCGGTTT1200               TCTTTGTATTTTTATTGCAGACTTTTAAATATGATAGGTATCTTGATGAAAACGGGAAGA1260               CAAAGACTACCTTCTATTGTAATGGACTCAAGTTAAAGTATTACTACATGCCCTTTGGAT1320               CGGGAGCTACAATATGTCCTGGAAGATTGTTCGCTATCCACGAAATCAAGCAATTTTTGA1380               TTCTGATGCTTTCTTATTTTGAATTGGAGCTTATAGAGGGCCAAGCTAAATGTCCACCTT1440               TGGACCAGTCCCGGGCAGGCTTGGGCATTTTGCCGCCATTGAATGATATTGAATTTAAAT1500               ATAAATTCAAGCATTTGTGAATACATGGCTGGAATAAGAGGACACTAGATATTACAGGAC1560               TGCAGAACACCCTCACCACACAGTCCCTTTGGACAAATGCATTTAGTGGTGGCACCACAC1620               AGTCCCTTTGGACAAATGCATTTAGTGGTGGTAGAAATGATTCACCAGGTCCAATGTTGT1680               TCACCAGTGCTTGCTTGTGAAATCTTAACATTTTGGTGACAGTTTCCAGATGCTATCACA1740               GACTCTGCTAGTGAAAAGAACTAGTTTCTAGGAGCACAATAATTTGTTTTCATTTGTATA1800               AGTCCATGAATGTTCATATAGCCAGGGATTGAAGTTTATTATTTTCAAAGGAAAACACCT1860               TTATTTTATTTTTTTTCAAAATGAAGATACACATTACAGCCAGGTGTGGTAGCAGGCACC1920               TGTAGTCTTAGCTACTCGAGAGGCCAAAGAAGGAGGATGCTTGAGCCCAGGAGTTCAAGA1980               CCAGCCTGGACAGCTTAGTGAGATCCCGTCTCCAAAGAAAAGATATGTATTCTAATTGGC2040               AGATTGTTTTTTCCTAAGGAAACTGCTTTATTTTTATAAAACTGCCTGACAATTATGAAA2100               AAATGTTCAAATTCACGTTCTAGTGAAACTGCATTATTTGTTGACTAGATGGTGGGGTTC2160               TTCGGGTGTGATCATATATCATAAAGGATATTTCAAATGTTATGATTAGTTATGTCTTTT2220               AATAAAAAGGAAATATTTTTCAACTTCTTCTATATCCAAAATTCAGGGCTTTAAACATGA2280               TTATCTTGATTTCCCAAAAACACTAAAGGTGGTTTT2316                                       __________________________________________________________________________ 

What is claimed is:
 1. Catalytically active, truncated human cholesterol 7α-hydroxylase (CYP7).
 2. Catalytically active, truncated human CYP7 which lacks a membrane anchor region that is present in human CYP7.
 3. A catalytically active, truncated human CYP7 according to claim 2, wherein said membrane anchor region comprises amino acids 1 to 24 of human CYP7.
 4. A catalytically active, truncated human CYP7 according to claim 1, wherein the truncated human CYP7 is capable of catalyzing, in the presence of reductase and NADPH, the initial hydroxylation of cholesterol at the 7α-position to form 7α-hydroxycholesterol.
 5. A catalytically active, truncated human CYP7 according to claim 4, wherein the truncated human CYP7 has a specific activity which is at least 10% of the specific activity of truncated rat CYP7. 